idle problems

Hi i recently posted on here regarding my mk1 golf cabrio it is a 1990 1.8gti kjet injection i had a problem with it misfiring from cold starts.  After finding out that the problem was the dizzy and a worn rotor arm the misfiring has now stopped but i still have a major problem with it not holding the revs when idling hot and cold and still struggles to start first time.  The revs are lower when cold and raise when it is warm i thought it should be the other way around because of the choke and if you rev and just let the revs drop it will stall or very nearly.  I have been reading through all the information in other posts with similar problems but still dont seem to be any closer to the answer can someone please help.  I dont particularly want to buy a new cold start valve just to try it.  Is there anything anyone can suggest to help me narrow down the problem.  Cheers

it could well be the aux air valve, as mine does the same with the revs increasing as it gets hotter. haynes tells you how to check the aav.