Document:

EXHIBIT 10.18

                                FIRST AMENDMENT

                                      to

                    AMENDED AND RESTATED GUARANTY AGREEMENT

                                      by

                              HOWELL CORPORATION,

                                 as Guarantor,

                                  in favor of

                               BANK OF MONTREAL,

                                   as Agent,

                         Effective as of July 26, 2001

<PAGE>

      This FIRST  AMENDMENT TO AMENDED AND RESTATED  GUARANTY  AGREEMENT  (this
"First  Amendment")  executed  effective  as of the  26th of  July,  2001  (the
"Effective  Date") is by HOWELL  CORPORATION,  a  corporation  formed under the
laws of the State of Delaware (the  "Guarantor")  in favor of BANK OF MONTREAL,
as agent for the Lenders (in such capacity,  together with its successors,  the
"Agent").

                                   Recitals

      A.   Howell Petroleum  Corporation,  a corporation  formed under the laws
of Delaware  (the  "Borrower"),  the Agents and the Lenders  entered  into that
certain  Credit  Agreement  dated as of December  17, 1997 (the "Prior  Credit
Agreement").

      B.   In order to secure the  obligations of the Borrower under the Credit
Agreement,  the Guarantor  entered into that certain  Guaranty  Agreement dated
as of December 17, 1997 (the "Prior Guaranty Agreement").

      C.   The  Borrower,  the Agents the  Lenders  entered  into that  certain
Amended  and  Restated  Credit  Agreement  dated as of  December  1,  1998 (the
"Amended and Restated  Credit  Agreement")  amending  and  restating  the Prior
Credit Agreement.

      D.   In order  to  secure  the  obligations  of the  Borrower  under  the
Amended  and  Restated  Credit  Agreement,  the  Guarantor  entered  into  that
certain  Amended and Restated  Guaranty  Agreement dated as of December 1, 1998
(the "Amended and Restated Guaranty Agreement").

      E.   The  Borrower  has  requested  and the Agents and the  Lenders  have
agreed  to  amend  certain  provisions  of  the  Amended  and  Restated  Credit
Agreement and the Amended and Restated Guaranty Agreement.

      F.   NOW,  THEREFORE,  in  consideration  of the  premises and the mutual
covenants herein contained,  for good and valuable  consideration,  the receipt
and sufficiency of which are hereby  acknowledged,  the parties hereto agree as
follows:

      Section 1.Defined Terms.  Each  capitalized  term which is defined in the
Amended and Restated Credit  Agreement,  but which is not defined in this First
Amendment,  shall  have the  meaning  ascribed  such  term in the  Amended  and
Restated   Credit   Agreement.   Unless   otherwise   indicated,   all  section
references in this First Amendment  refer to the Amended and Restated  Guaranty
Agreement.

      Section 2.Amendments to the Amended and Restated GuarantyAgreement.

      2.1  Amendments to Section 1.2. The  following  new  definition is hereby
           -------------------------
added where alphabetically appropriate:

           "Net Cash  Proceeds"  shall mean,  with  respect to any sale or
      disposition  of  securities,   the  cash  proceeds  (including  cash
      equivalents  and  any  cash  payments  received  by way of  deferred
      payment of principal  pursuant to a note or  installment  receivable
      or purchase price  adjustment  receivable or otherwise,  but only as
      and when  received)  of such sale or other  disposition  received by
      the Guarantor or any of its  Consolidated  Subsidiaries,  net of all
      attorneys'  fees,  accountants'  fees,  investment  banking fees and
      other  customary  fees  and  commissions  actually  incurred  by the
      Guarantor or any of its Consolidated  Subsidiaries and documented in
      connection therewith.

      2.2  Amendments  to  Section  5.3.  Section  5.3  is  hereby  amended  by
deleting  such  section in its  entirety  and  inserting  in lieu  thereof  the
following:

           5.3  Minimum   Tangible  Net  Worth.  The  Guarantor  will  not
      permit  its  Tangible  Net Worth at any time to be less than the sum
      (without  duplication)  of (i)  $33,050,000  (85% of the Guarantor's
      Tangible  Net Worth as of December 31,  2000),  plus (ii) 50% of the
      Net Cash  Proceeds  of any primary  offering  (public or private) of
      equity  securities  consummated  by the  Guarantor  after  the First
      Amendment  Effective Date, plus (iii) 50% of Consolidated Net Income
      for each fiscal  quarter of the Guarantor  ending after December 31,
      2000 (to the extent for any such  fiscal  quarter  Consolidated  Net
      Income is positive).

      2.3  Amendments  to  Section  5.4.  Section  5.4  is  hereby  amended  by
deleting  such  section in its  entirety  and  inserting  in lieu  thereof  the
following:

           5.4  Current Ratio.  The Guarantor's  ratio of (i) consolidated
      current  assets  plus  availability   under  the  Facility  to  (ii)
      consolidated  current  liabilities  (excluding current maturities of
      the Notes) shall not at any time be less than 1.0 to 1.0.

      Section 3.Miscellaneous.
                -------------

      3.1  Confirmation.  The  provisions of the Amended and Restated  Guaranty
Agreement (as amended by this First  Amendment)  shall remain in full force and
effect in accordance with its terms following the  effectiveness  of this First
Amendment.

      3.2  Counterparts.  This First  Amendment  may be executed by one or more
of the parties hereto in any number of separate  counterparts,  and all of such
counterparts  taken  together  shall be deemed to  constitute  one and the same
instrument.

      3.3  No Oral  Agreement.  THIS WRITTEN FIRST  AMENDMENT,  THE AMENDED AND
RESTATED  GUARANTY   AGREEMENT  AND  THE  OTHER  LOAN  DOCUMENTS   EXECUTED  IN
CONNECTION  HEREWITH AND THEREWITH  REPRESENT THE FINAL  AGREEMENT  BETWEEN THE
PARTIES AND MAY NOT BE CONTRADICTED BY EVIDENCE OF PRIOR,  CONTEMPORANEOUS,  OR
UNWRITTEN  ORAL  AGREEMENTS  OF  THE  PARTIES.  THERE  ARE NO  SUBSEQUENT  ORAL
AGREEMENTS BETWEEN THE PARTIES.

      3.4  Governing  Law.  THIS FIRST  AMENDMENT  (INCLUDING,  BUT NOT LIMITED
           --------------
TO,  THE  VALIDITY  AND  ENFORCEABILITY  HEREOF)  SHALL  BE  GOVERNED  BY,  AND
CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF TEXAS.

<PAGE>

                [SIGNATURE PAGE - FIRST AMENDMENT TO
                   AMENDED AND RESTATED GUARANTY AGREEMENT]

      IN WITNESS  WHEREOF,  the parties hereto have caused this First Amendment
to be duly executed effective as of the date first written above.

GUARANTOR:                                          HOWELL CORPORATION

                               By:   /s/ ALLYN R. SKELTON
                                     --------------------
                                     Allyn R. Skelton, Vice President &
                                     Chief Financial Officer

AGENT:                         BANK OF MONTREAL, AS AGENT

                               By:   /s/ JAMES DUCOTE
                                     -----------------------------
                                     James Ducote, Vice PresidentExhibit 10.11

                           CHANGE OF CONTROL AGREEMENT

            This CHANGE OF CONTROL AGREEMENT is dated as of ______________
between ANAREN MICROWAVE, INC., a New York Corporation ("Anaren"), and
____________________________ ("Employee"). The term "Anaren" shall mean all of
its subsidiaries, whether directly or indirectly owned.

                                    Recitals

      A.    Employee is currently employed by Anaren in a senior management
            capacity.

      B.    Anaren desires to retain the services of Employee and to induce
            Employee to remain with Anaren.

      C.    In consideration of the agreements of the parties contained in this
            Agreement, and intending to be legally bound by the terms of this
            Agreement, the parties agree as follows:

                                      Terms

1.    Term of Agreement.

      The term of this Agreement shall be for the period from the date of the
Agreement to June 30, 2006 and shall automatically expire effective June 30,
2006, unless otherwise renewed by the parties.
<PAGE>

2.    Change of Control.

      (a) Subject to the limitations described in paragraphs 2(d), (e), (f) and
(g), if Employee's employment by Anaren shall cease for any reason, but not
including Employee's voluntary termination or Employee's termination for "cause"
(as defined in paragraph 3), within 1 year following a "Change of Control" that
occurs during the term of this Agreement, Anaren shall:

            (i) Pay to Employee an aggregate severance benefit equal to (A) 100
percent of Employee's then current Base Annual Salary, plus (B) an amount equal
to the management incentive bonus paid to Employee in the year previous to the
year during which the "Change of Control" occurs; and

            (ii) Treat as immediately exercisable all options granted by Anaren
to Employee to acquire Anaren common stock that are not exercisable or that have
not been exercised, so as to permit Employee to purchase the balance of Anaren
stock not yet purchased until the end of the exercise period provided in the
original grant of the option right; and

            (iii) Treat as immediately vested all restricted Anaren stock, if
any, held by Employee; and

            (iv) Provide Employee with continuation of life and health insurance
benefits, under the same terms and conditions that Anaren provides such
insurance to its active employees, until payments under paragraph 2(a)(i) above
have been paid in full.

      (b) The severance benefit payable under paragraph 2(a)(i) above shall be
payable in substantially equal installments over a period of twelve months.
<PAGE>

      (c) Upon expiration of the period described in paragraph 2(a)(iv),
Employee (and Employee's qualified beneficiaries) shall be eligible to commence
COBRA continuation benefits.

      (d) In no event shall the aggregate of all amounts paid to or value
received by Employee following a "Change of Control" (whether paid or received
pursuant to this paragraph 2 or otherwise) exceed the maximum aggregate amount
or value that could be paid to, or received by, Employee without such aggregate
amount being treated as a "parachute payment" within the meaning of Internal
Revenue Code Section 280G.

      (e) Anaren shall not be obligated to provide or continue the payments
specified in paragraph 2(a)(i) above, if Anaren, within the one-year period
following such Change of Control, provides Employee, and Employee accepts, a
position within Anaren's organization of comparable responsibility and
compensation. Anaren shall allow Employee to maintain such alternative position
for a period of not less than one year from the date of acceptance.

      (f) Payments made and benefits provided pursuant to this paragraph 2 shall
be subject to withholding for income, employment and other similar taxes Anaren
may be required to withhold.

      (g) As a condition to Anaren's obligation to provide the payments and
benefits pursuant to this paragraph 2, Employee must first execute a General
Release, that releases and discharges Anaren from all claims of any type arising
out of Employee's employment or the termination of his employment.

      (h) For purposes of paragraph 2(a), a "Change of Control," shall be deemed
to have occurred if:
<PAGE>

            (i) any "person," including a "group" as determined in accordance
with the Section 13(d)(3) of the Securities Exchange Act of 1934 ("Exchange
Act"), is or becomes the beneficial owner, directly or indirectly, of securities
of Anaren representing 30% or more of the combined voting power of Anaren's then
outstanding securities;

            (ii) as a result of, or in connection with, any tender offer or
exchange offer, merger or other business combination (a "Transaction"), the
persons who were directors of Anaren before the Transaction shall cease to
constitute a majority of the Board of Directors of Anaren or any successor;

            (iii) Anaren is merged or consolidated with another corporation and
as a result of the merger or consolidation less than 70% of the outstanding
voting securities of the surviving or resulting corporation shall then be owned
in the aggregate by the former stockholders of Anaren, other than (A) affiliates
within the meaning of the Exchange Act, or (B) any party to the merger or
consolidation;

            (iv) a tender offer or exchange offer is made and consummated for
the ownership of securities of Anaren representing 30% or more of the combined
voting power of Anaren's then outstanding voting securities;

            (v) Anaren transfers substantially all of its assets to another
corporation which is not controlled by Anaren; or

            (vi) Any tender offer or exchange offer, merger or other business
combination not approved by two-thirds of the members of the Board of Directors
in office immediately prior to such event.
<PAGE>

3.    Termination "For Cause".

      (a) Notwithstanding any contrary provision contained in paragraph 2,
Anaren may terminate this Agreement "for cause" (defined below) at any time,
effective upon receipt by Employee of written notice of termination. Upon
termination of employment "for cause," Employee shall be entitled only to the
salary due Employee from Anaren to the date of receipt by Employee of written
notice of termination.

      (b) Termination "for cause" for purposes of this Agreement shall include,
but not be limited to, any of the following:

            (i) any act of fraud or the commission of a felony; or

            (ii) breach of duty or obligation to Anaren or receipt of financial
or other economic profit or gain as a result of or in any way arising out of
Employee's position with Anaren and failure to account to Anaren for such
profits or other gains;

            (iii) disclosure of confidential or private Anaren information or
aiding a competitor of Anaren (or any affiliate of Anaren) to the detriment of
Anaren (or any affiliate of Anaren); or

            (iv) the employees unreasonable neglect or refusal to perform the
material duties of his position or intentional material damage to the business
of Anaren.

4.    Covenants.

      (a) Confidentiality. Employee shall not, without the prior written consent
of Anaren, disclose or use in any way, either during his employment by Anaren or
thereafter, except as required in the course of his employment by Anaren, any
confidential business or technical information or trade secrets acquired in the
course of Employee's employment by Anaren. Employee acknowledges and agrees that
it would be difficult to fully compensate Anaren for
<PAGE>

damages resulting from the breach or threatened breach of the foregoing
provision and, accordingly, that Anaren shall be entitled to temporary
preliminary injunctions and permanent injunctions to enforce this provision.
Anaren's right to obtain injunctive relief shall not, however, diminish Anaren's
right to claim and recover damages. Employee commits to use his best efforts to
prevent the publication or disclosure of any trade secret or any confidential
information concerning the business or finances of Anaren or Anaren's
subsidiaries, or any of its or their dealings, transactions or affairs which may
come to Employee's knowledge in the pursuance of its duties on behalf of Anaren.

      (b) No Competition. Employee's employment is subject to the condition that
during the term of his employment and for a period of twelve (12) months from
the date of the termination of his employment (the "Date of Termination")
Employee shall not, directly or indirectly, own, manage, operate, control or
participate in the ownership, management, operation or control of or be
connected as an officer, employee, partner, director, individual proprietor,
lender, consultant or otherwise, or have any financial interest in, or aid or
assist anyone else in the conduct of any entity or business ("a Competitive
Operation") which principal business directly competes with Anaren on the Date
of Termination. Ownership by Employee of not more than 5% of the voting stock of
any publicly held corporation shall not constitute a violation of this
paragraph.

      (c) Termination of Payments. Upon the breach by Employee of any covenant
under this paragraph 4, Anaren may offset and/or recover from Employee
immediately any and all of the severance compensation paid to Employee under
subparagraph 2(a)(1) hereof in addition to any and all other remedies available
to Employer under law or in equity.
<PAGE>

5.    Miscellaneous.

      (a) Notices. Any and all notices with respect to this Agreement shall be
sufficient if furnished personally in writing or sent by certified mail, return
receipt requested, to the last known address or other address designated by the
parties to this Agreement.

      (b) Entire Agreement; Release From Prior Agreements. This Agreement
represents the entire agreement between the parties and specifically supersedes
any and all oral or written agreements previously entered into by the parties,
and each party releases the other party of all obligations and liabilities with
respect to any prior employment agreements between the parties.

      (c) Governing Law. This Agreement, having been made and duly executed
within the State of New York, shall be construed and governed in accordance with
and pursuant to New York law.

      (d) Waiver. In the event that any breach of this Agreement by Employee or
Anaren is waived by act or failure to act, such waiver shall not constitute a
waiver of any subsequent breach by either party.

      (e) Severability. If any provision of this Agreement shall be held invalid
or unenforceable, such invalidity or unenforceability shall affect only that
particular provision and shall not affect or render invalid or unenforceable any
other provision of this Agreement, and this Agreement shall be carried out as if
any such invalid or unenforceable provision were not a part of the Agreement.

      (f) Binding Effect. This Agreement shall be binding upon and shall inure
to the benefit of the successors, assigns, legal representatives and heirs of
the parties.

      (g) Arbitration and Fees. Any dispute between the parties relating to the
terms of this Agreement, or any interpretation, construction or enforcement
hereof, shall first be submitted to
<PAGE>

non-binding arbitration in Syracuse, New York in accordance with the rules and
regulations of the American Arbitration Association then in effect. Each party
shall be responsible for its own costs and expenses in pursuing non-binding
arbitration, and any arbitration fees or costs shall be shared equally between
the parties. However, if Employee is a party in an arbitration to collect
payments due pursuant to this Agreement and prevails in collecting payments due
in the arbitration or settlement of the arbitration, Anaren shall reimburse
Employee for reasonable attorneys' fees incurred by Employee in connection with
such arbitration.

      IN WITNESS WHEREOF, the parties have signed this Agreement after full
opportunity to read and discuss the provisions of the Agreement, and both
parties voluntarily assent to this Agreement with full understanding of its
provisions.

                                     EMPLOYEE

                                     ----------------------------------
                                     (Name of Employee)

                                     ANAREN MICROWAVE, INC.

                                     By:
                                        -------------------------------
                                              Lawrence A. Sala
                                              President & CEO

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