Exhibit 4.6


Amendment, effective June 11, 2003 of Clean Diesel Technologies 1994
Incentive Plan:

          . . . .

          6.1 (a) Options shall be Non-Qualified Stock Options or Incentive
          Stock Options.

          . . . .

          6.1 (h) Incentive Stock Options


          (i)  Each Incentive Stock Option shall not have an aggregate Fair
               Market Value Per Share  (determined for each Incentive Stock
               Option at its grant  date) of Shares  with  respect to which
               Incentive  Options are  exercisable  for the first time by a
               Participant during any calendar year (under the Plan and any
               other  stock   option  plan  of  the   Corporation   or  its
               Subsidiaries ("Other Plans")), determined in accordance with
               the  provisions  of Section 422 of the Code,  which  exceeds
               $100,000;

          (ii) To the extent that the aggregate Fair Market Value Per Share
               of stock  with  respect  to which  Incentive  Stock  Options
               granted  under the Plan and any Other Plans are  exercisable
               by a Participant for the first time during any calendar year
               exceeds  $100,000,  such  Incentive  Stock  Options shall be
               treated  as  Non-Qualified   Stock  Options  to  the  extent
               necessary so that such aggregate Fair Market Value per Share
               of Stock  does not  exceed  $100,000.  For  purposes  of the
               foregoing sentence, Incentive Stock Options shall be treated
               as  Non-Qualified  Stock  Options  according to the order in
               which they were granted such that the most recently  granted
               Incentive  Stock Options are first treated as  Non-Qualified
               Stock Options; and

          (iii)Each  Incentive  Stock Option shall require the  Participant
               to notify the Board or the Committee of any  disposition  of
               any Shares issued  pursuant to the exercise of the Incentive
               Stock  Option under the  circumstances  described in Section
               421  of  the  Code   (relating   to  certain   disqualifying
               dispositions) within ten (10) days of such disposition.

          . . . .