<PAGE>

                                                                   EXHIBIT 10.27


                                                                            Gant






                                December 1, 2000



Mr. Richard A. Parlontieri
Emissions Testing, Inc.
400 Colony Park
Building 104, Suite 600
Cumming, Georgia  30041

          Re:  Letter Agreement Regarding 100,000 Shares of the Common Stock of
               Emissions Testing, Inc., a Georgia Corporation (the "Company"),
               Owned of Record by Gant Alumni Associates, LLC ("Gant Alumni")

Dear Mr. Parlontieri:

     As you know, Gant Alumni is the owner of record of 100,000 shares of the
common stock, no par value per share, of the Company.

     The Company has filed a registration statement on Form S-1 (the
"Registration Statement") with the Securities and Exchange Commission (the
"SEC") for the registration of certain shares of the Company's common stock
("Common Stock"), in a public offering (the "Offering") under the Securities Act
of 1933, as amended (the "Act"). Among the shares of Common Stock to be
registered in the Offering are 100,000 shares of Common Stock owned of record by
Gant Alumni ( the "Registered Shares").

     Inasmuch as Gant Alumni wishes to induce the Company to continue its
efforts in connection with the Offering, Gant Alumni hereby agrees with, and
represents to, the Company that Gant Alumni will not, directly or indirectly,
sell, offer to sell, grant an option for the sale of, assign, transfer, pledge,
hypothecate or otherwise encumber or dispose of in any manner, any of the
Registered Shares (or any interest therein), INCLUDING, WITHOUT LIMITATION,
PURSUANT TO RULE 144 OR RULE 144A UNDER THE ACT, from and after the date hereof
except as follows: The Company agrees that Gant Alumni shall have the right to
sell, offer to sell, grant an option for the sale of, assign, transfer, pledge,
hypothecate or otherwise encumber and/or dispose of in any manner, all or any
part of the Registered Shares at any time after the earlier of (I) 12:01 AM
(Atlanta, Georgia time) on October 1, 2001, or (II) the date and time that the
Company has reduced to $250,000 or below the outstanding aggregate principal
amount of the Company's indebtedness to GCA Strategic Investment Fund Limited, a
Bermuda corporation ("GCA") (or its assignees) under the convertible debentures
issued and sold (before or after the date hereof)

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Emissions Testing, Inc.
December 1, 2000
Page 2


by the Company pursuant to the terms of that certain Securities Purchase
Agreement dated effective as of June 1, 2000 between the Company and GCA, as the
same may be amended from time to time.

     Gant Alumni agrees and understands that:

          (a)  Any sale or other transaction involving all or any part of
               Registered Shares are, and shall hereafter remain, subject to all
               applicable federal and state securities laws and regulations.

          (b)  The Company may place a legend reflecting this letter and terms
               hereof on any certificate evidencing all or any part of the
               shares described herein, and may give written notice of this
               letter, and the terms hereof, to the Company's transfer agent;

          (c)  This letter, and the terms hereof, shall be binding upon Gant
               Alumni and the successors and assigns of Gant Alumni; and

          (d)  The Company is relying upon the agreements and representations of
               Gant Alumni set forth in this letter in filing the Registration
               Statement and amendments thereto and in consummating the
               Offering.

     The Company agrees that, upon the occurrence of the event described in
clause (II) above, the Company shall give prompt written notice thereof to Gant
Alumni at the last known address then available to the Company.

     The parties hereto agree that this Letter Agreement shall not be amended,
modified or terminated without the prior written consent of GCA, which consent
may be granted or denied in the sole discretion of GCA.

     If the foregoing meets with your understanding of our agreement, please so
signify by signing and returning this Letter Agreement to us.


<TABLE>
<S>                                 <C>
                                    Very truly yours,

                                    GANT ALUMNI ASSOCIATES, LLC


                                    By: /s/ Alex DeMars
                                       ---------------------------------------
                                      Name: Alex DeMars
                                           -----------------------------------
                                       Position: Managing Partner
                                                ------------------------------
</TABLE>


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Emissions Testing, Inc.
December 1, 2000
Page 3



Agreed to and accepted as of the
day and year first above written.

EMISSIONS TESTING, INC.



By: /s/ Rich Parlontieri
    ------------------------------
   Name: Rich Parlontieri
         -------------------------
   Position: President/CEO
            ----------------------