[356RS]

I would really like to figure this problem out. I lot of help here and you have checked almost everything you can with the tools you have. I have read all the posts and keep going back to the fact that your car runs fine, starts cold, runs great warm but ends up with idle at 2000. A lot of posts suggest TB's, linkage and or air/vacuum leaks. This would diffidently cause the idle to go up after warm up. The odd thing is that it seems to happen very fast at a point during warm up if I'm understanding your posts correctly. Is there something happening in the thermostat during warm up? I don't think so. Any problems inside the thermostat will either keep it from extending and run very rich, or after warm up get stuck extended and never return for cold start. Or is the thermostat lever to balance bar inside the pump causing some problem? Is there something inside the MFI pump that can all of a sudden during warm up take things up to 2000 rpm at idle? Lots of possibilities, no answer. There is one thing that you did that brought the engine back to idle. You pushed on the main rack, giving the system more fuel and it seemed to like it. Was this added fuel masking some air/vacuum leaks? I made a suggestion toward the beginning of this to take a few turns CCW on the main rack. What I wanted to see was #1, will it now keep a low idle? #2, same thing happens again but with a little lower rpm instead of 2000. Doing this will help on figuring the problem out. It might help to eliminate the pump. Give it a try, what can you loose.

p.s. If you do this adjustment on the main rack, do it after warm up and try 6 clicks CCW.