Exhibit 2.1**AMENDMENT NO. 1 TO AGREEMENT AND PLAN OF MERGER**          AMENDMENTNO. 1, dated as of June 25, 2007 (this “Amendment”), to the Agreement andPlan of Merger, dated as of February 5, 2007 (the “Merger Agreement”), among HanoverCompressor Company, a Delaware corporation (“Hanover”), Universal Compression Holdings,Inc., a Delaware corporation (“Universal”), Exterran Holdings, Inc., a Delaware corporation(formerly known as Iliad Holdings, Inc.) (“Holdco”), Hector Sub, Inc., a Delawarecorporation and a wholly owned subsidiary of Holdco, and Ulysses Sub, Inc., a Delaware corporationand a wholly owned subsidiary of Holdco.**RECITALS**          WHEREAS the parties hereto are parties to the Merger Agreement, pursuant to which, upon theterms and subject to the conditions set forth therein, the parties intend to effect the mergertransactions described in Sections 1.1 and 1.2 thereof, so that thereafter each of Hanover andUniversal will be wholly owned by Holdco; and          WHEREAS the parties hereto wish to amend the Merger Agreement as provided herein in order toprovide (i) that the Closing shall occur on a date specified by the parties, but in any event nolater than the third business day immediately following the date of fulfillment or waiver of thelast to be fulfilled or waived of the conditions set forth in Section 8.1 of the Merger Agreement,(ii) that the certificate of incorporation and bylaws of each of Universal and Hanover in effect asof the Initial Effective Time and the Effective Time, respectively, will be amended as set forth onexhibits to the Merger Agreement, and (iii) for the implementation at the Closing of a directregistration system permitting ownership of Holdco Common Stock without the issuance or holding ofstock certificates;          NOW, THEREFORE, in consideration of the premises, the mutual agreements hereinafter containedand for other good and valuable consideration, the receipt and sufficiency of which are herebyacknowledged, the parties hereto agree that, effective as of the date of this Amendment, the MergerAgreement shall be amended as follows:**ARTICLE 1****DEFINITIONS**     1. Definitions. Unless otherwise defined herein, capitalized terms used in thisAmendment shall have the respective meaning ascribed to such terms in the Merger Agreement.**ARTICLE 2****AMENDMENTS TO THE MERGER AGREEMENT**     1. Amendment to Article I of the Merger Agreement. Section 1.3 of the MergerAgreement is hereby amended and restated in its entirety to read as follows:     “Section 1.3 *The Closing*. Upon the terms and subject to the conditions setforth in this Agreement, the closing of the Mergers (the “Closing”) shall take placeat the offices of Baker Botts L.L.P., One Shell Plaza, 910 Louisiana, Houston, Texas77002, at 9:00 a.m., local time, on a date to be specified by the
 

 
parties, which shall be no later than the third business day immediatelyfollowing the date of fulfillment or waiver (in accordance with the provisionshereof) of the last to be fulfilled or waived of the conditions set forth in Section8.1, or, if on such day any condition set forth in Section 8.2 or Section 8.3 hasnot been fulfilled or waived (in accordance with the provisions hereof) (other thanthose conditions that by their nature are to be fulfilled at the Closing, butsubject to the fulfillment or waiver of such conditions), as soon as practicableafter all the conditions set forth in Article 8 have been fulfilled or waived inaccordance herewith. The date on which the Closing occurs is hereinafter referredto as the “Closing Date.””     2. Amendments to Article II of the Merger Agreement.          (a) Section 2.1 of the Merger Agreement is hereby amended and restated in its entirety to readas follows:     “Section 2.1 *Certificates of Incorporation of the Surviving Entities*. As ofthe Initial Effective Time, the certificate of incorporation of Universal as ineffect immediately prior to the Initial Effective Time shall be amended to read inits entirety as set forth on Exhibit 2.1.1 hereto and, as so amended, shall be thecertificate of incorporation of the Universal Surviving Entity, until duly amendedin accordance with Applicable Laws. As of the Effective Time, the certificate ofincorporation of Hanover as in effect immediately prior to the Effective Time shallbe amended to read in its entirety as set forth on Exhibit 2.1.2 hereto and, as soamended, shall be the certificate of incorporation of the Hanover Surviving Entity,until duly amended in accordance with Applicable Laws.”          (b) Section 2.2 of the Merger Agreement is hereby amended and restated in its entirety to readas follows:     “Section 2.2 *Bylaws of the Surviving Entities*. As of the Initial EffectiveTime, the bylaws of Universal as in effect immediately prior to the InitialEffective Time shall be amended and restated to read in their entirety as set forthon Exhibit 2.2.1 hereto and, as so amended, shall be the bylaws of the UniversalSurviving Entity, until duly amended in accordance with Applicable Laws. As of theEffective Time, the bylaws of Hanover as in effect immediately prior to theEffective Time shall be amended and restated to read in their entirety as set forthon Exhibit 2.2.2 hereto and, as so amended, shall be the bylaws of the HanoverSurviving Entity, until duly amended in accordance with Applicable Laws.”     2. Amendment to Article IV of the Merger Agreement. Section 4.2 of the MergerAgreement is hereby amended by adding the following to the end thereof:“(i) Notwithstanding anything to the contrary herein, the parties intend that Holdcowill implement a direct registration system at the Closing, and if such directregistration system is implemented by Holdco at such time, all shares of
2

 
Holdco Common Stock shall be in uncertificated book-entry form unless a physicalcertificate is requested in writing by a holder of Certificates.”     3. Amendments to the Exhibits to the Merger Agreement.          (a) The form of Restated Certificate of Incorporation of Universal attached hereto asAnnex A shall be attached as a new Exhibit 2.1.1 to the Merger Agreement.          (b) The form of Certificate of Incorporation of Hanover attached hereto as Annex Bshall be attached as a new Exhibit 2.1.2 to the Merger Agreement.          (c) The form of Second Restated Bylaws of Universal attached hereto as Annex C shallbe attached as a new Exhibit 2.2.1 to the Merger Agreement.          (d) The form of Second Amended and Restated Bylaws of Hanover attached hereto as AnnexD shall be attached as a new Exhibit 2.2.2 to the Merger Agreement.**ARTICLE 3****MISCELLANEOUS**     1. Effect on the Merger Agreement. The Merger Agreement shall remain in full forceand effect and, as amended by this Amendment, is hereby ratified and affirmed in all respects. Onand after the date hereof, each reference in the Merger Agreement to “this Agreement,” “herein,”“hereunder” or words of similar import shall mean and be a reference to the Merger Agreement asamended by this Amendment.     2. Assignment; Binding Effect; Benefit. Neither this Amendment nor any of the rights,interests or obligations hereunder shall be assigned by any of the parties hereto (whether byoperation of law or otherwise) without the prior written consent of the other parties. Subject tothe preceding sentence, this Amendment shall be binding upon and shall inure to the benefit of andbe enforceable by the parties hereto and their respective successors and assigns. Nothing in thisAmendment, expressed or implied, is intended to confer on any person other than the parties heretoor their respective heirs, successors, executors, administrators and assigns any rights, remedies,obligations or liabilities under or by reason of this Amendment.     3. Governing Law.**This Amendment and the rights and obligations of the parties heretoshall be governed by and construed and enforced in accordance with the laws of the State ofDelaware without regard to the conflicts of law provisions thereof that would cause the laws of anyother jurisdiction to apply.**     4. Counterparts. This Amendment may be executed by the parties hereto in separatecounterparts, each of which when so executed and delivered shall be an original, but all suchcounterparts shall together constitute one and the same instrument. Each counterpart may consistof a number of copies hereof each signed by less than all, but together signed by all of theparties hereto.     5. Headings. Headings of the Articles and Sections of this Amendment are for theconvenience of the parties only and shall be given no substantive or interpretative effectwhatsoever.
3

 
     6. Severability. If any provision of this Amendment is invalid, illegal orunenforceable, that provision will, to the extent possible, be modified in such a manner as to bevalid, legal and enforceable but so as to retain most nearly the intent of the parties as expressedherein, and if such a modification is not possible, that provision will be severed from thisAmendment, and in either case the validity, legality and enforceability of the remaining provisionsof this Amendment will not in any way be affected or impaired thereby. If any provision of thisAmendment is so broad as to be unenforceable, the provision shall be interpreted to be only sobroad as is enforceable.
4

 
The parties have caused this Amendment to be signed by their respective officers thereuntoduly authorized as of the date first written above.         HANOVER COMPRESSOR COMPANY           By: /s/ John E. Jackson           Name: John E. Jackson    Title: President and Chief Executive Officer           UNIVERSAL COMPRESSION HOLDINGS, INC.           By: /s/ Stephen A. Snider           Name: Stephen A. Snider    Title: Chief Executive Officer           EXTERRAN HOLDINGS, INC.           By: /s/ Stephen A. Snider           Name: Stephen A. Snider    Title: Sole Director           HECTOR SUB, INC.           By: /s/ J. Michael Anderson           Name: J. Michael Anderson    Title: Sole Director           ULYSSES SUB, INC.           By: /s/ J. Michael Anderson           Name: J. Michael Anderson    Title: Sole Director  
 

 
Annex A**RESTATED CERTIFICATE OF INCORPORATION****of****UNIVERSAL COMPRESSION HOLDINGS, INC.**          FIRST: The name of the corporation is Universal Compression Holdings, Inc.          SECOND: The address of the corporation’s registered office in the State of Delaware is 1209Orange Street in the City of Wilmington, County of New Castle, 19801. The name of its registeredagent at such address is The Corporation Trust Company.          THIRD: The purpose of the corporation is to engage in any lawful act or activity for whichcorporations may be organized under the General Corporation Law of the State of Delaware (the“DGCL”).          FOURTH: The total number of shares of all classes of stock which the corporation shall haveauthority to issue is 100 shares of common stock, par value $0.01 per share.          FIFTH: The number of directors of the corporation shall be as from time to time specified in,or determined in the manner provided in, the Bylaws. Election of directors need not be by writtenballot unless the Bylaws so provide.          SIXTH: In furtherance of, and not in limitation of, the powers conferred by statute, the Boardof Directors is expressly authorized to make, adopt, amend, alter or repeal the Bylaws of thecorporation.          SEVENTH: No director of the corporation shall be personally liable to thecorporation or its stockholders for monetary damages for breach of fiduciary duty asa director, except for liability (i) for any breach of the director’s duty ofloyalty to the corporation or its stockholders, (ii) for acts or omission not ingood faith or which involve intentional misconduct or a knowing violation of law,(iii) under Section 174 of the DGCL or (iv) for any transaction from which thedirector derived an improper personal benefit. If the DGCL is amended after thedate of filing of this certificate ofincorporation to authorize corporate action further eliminating or limiting thepersonal liability of directors, then the liability of a director of thecorporation, in addition to the limitation on personal liability provided herein,shall be limited to the fullest extent permitted by the DGCL as amended. Any repealor modification of this Article shall not adversely affect any limitation on theliability of a director existing at the time of such repeal or modification.
 

 
          EIGHTH: Whenever a compromise or arrangement is proposed between this corporationand its creditors or any class of them and/or between this corporation and itsstockholders or any class of them, any court of equitable jurisdiction within theState of Delaware may, on the application in a summary way of this corporation or ofany creditor or stockholder thereof or on the application of any receiver orreceivers appointed for this corporation under Section 291 of the DGCL or on theapplication of trustees in dissolution or of any receiver or receivers appointed forthis corporation under Section 279 of the DGCL order a meeting of the creditors orclass of creditors, and/or of the stockholders or class of stockholders of thiscorporation, as the case may be, to be summoned in such manner as the said courtdirects. If a majority in number representing three-fourths in value of thecreditors or class of creditors, and/or of the stockholders or class of stockholdersof this corporation, as the case may be, agree to any compromise or arrangement andto any reorganization of this corporation as a consequence of such compromise orarrangement, the said compromise or arrangement and the said reorganization shall,if sanctioned by the court to which the said application has been made, be bindingon all the creditors or class of creditors, and/or on all the stockholders or classof stockholders, of this corporation, as the case may be, and also on thiscorporation.
2

 
Annex B**CERTIFICATE OF INCORPORATION****of****HANOVER COMPRESSOR COMPANY**          FIRST: The name of the corporation is Hanover Compressor Company.          SECOND: The address of the corporation’s registered office in the State of Delaware is 1209Orange Street in the City of Wilmington, County of New Castle, 19801. The name of its registeredagent at such address is The Corporation Trust Company.          THIRD: The purpose of the corporation is to engage in any lawful act or activity for whichcorporations may be organized under the General Corporation Law of the State of Delaware (the“DGCL”).          FOURTH: The total number of shares of all classes of stock which the corporation shall haveauthority to issue is 100 shares of common stock, par value $0.01 per share.          FIFTH: The number of directors of the corporation shall be as from time to time specified in,or determined in the manner provided in, the Bylaws. Election of directors need not be by writtenballot unless the Bylaws so provide.          SIXTH: In furtherance of, and not in limitation of, the powers conferred by statute, the Boardof Directors is expressly authorized to make, adopt, amend, alter or repeal the Bylaws of thecorporation.          SEVENTH: No director of the corporation shall be personally liable to thecorporation or its stockholders for monetary damages for breach of fiduciary duty asa director, except for liability (i) for any breach of the director’s duty ofloyalty to the corporation or its stockholders, (ii) for acts or omission not ingood faith or which involve intentional misconduct or a knowing violation of law,(iii) under Section 174 of the DGCL or (iv) for any transaction from which thedirector derived an improper personal benefit. If the DGCL is amended after thedate of filing of this certificate ofincorporation to authorize corporate action further eliminating or limiting thepersonal liability of directors, then the liability of a director of thecorporation, in addition to the limitation on personal liability provided herein,shall be limited to the fullest extent permitted by the DGCL as amended. Any repealor modification of this Article shall not adversely affect any limitation on theliability of a director existing at the time of such repeal or modification.
 

 
          EIGHTH: Whenever a compromise or arrangement is proposed between this corporationand its creditors or any class of them and/or between this corporation and itsstockholders or any class of them, any court of equitable jurisdiction within theState of Delaware may, on the application in a summary way of this corporation or ofany creditor or stockholder thereof or on the application of any receiver orreceivers appointed for this corporation under Section 291 of the DGCL or on theapplication of trustees in dissolution or of any receiver or receivers appointed forthis corporation under Section 279 of the DGCL order a meeting of the creditors orclass of creditors, and/or of the stockholders or class of stockholders of thiscorporation, as the case may be, to be summoned in such manner as the said courtdirects. If a majority in number representing three-fourths in value of thecreditors or class of creditors, and/or of the stockholders or class of stockholdersof this corporation, as the case may be, agree to any compromise or arrangement andto any reorganization of this corporation as a consequence of such compromise orarrangement, the said compromise or arrangement and the said reorganization shall,if sanctioned by the court to which the said application has been made, be bindingon all the creditors or class of creditors, and/or on all the stockholders or classof stockholders, of this corporation, as the case may be, and also on thiscorporation.          NINTH: The name and mailing address of the incorporator is:Janis I. Rohrer