My 97 1.8 A4 isn't coming back down to idle as it should, if you give it gas it comes down, alsmost stalls, then kinda rumbles, sometimes idles real low, sometimes goes back to idle. Can't find an idle adjustment, if I hold it with my foot when it comes down from a rev, it idles, so it seems if I could adjust it, it would be OK. I do have a larger Garret turbo on there, don't know if there's some other idle controller I can't see. Any ideas?

 

You should try doing a TBA. Look for my thread about my idle issues and how I solved them, from about 1-2 weeks ago.

 

Also look into cleaning the ICV (Idle control valve) and the throttle body as well. Same problems with mine and it cured it. Also my 2 flex plastic tubes underneath the throttle body were horribly frothed up and plugged. Pita to get back on though cause the o-rings swelled up from the cleaning.