my car has a problem with this too...im running a 16V from 88 and ive talked to a few people, wht they think (since mine isnt carbed, [Im fuel injected]) is that it could be a Cold Idle Valve...now I've heard that these are on Hondas and some other Japanese Cars but i havent heard of them being on VW's or Audis or anything like that....if they are i would say thats what it is...i would check that if thats the case.