I take it the throttle is sticking at 2000rpm just briefly after a cold start?
I've got throttle issues as well. It rarely fast idles (1200rpm) and when it does, it shoots up to 2000 for a second then drops to 1200.
Already cleaned and polished the throttle, but I saw gouges in the main body where the blade was rubbing it. The throttle also squeaks when moved by hand, so I think it's fecked.
I'm going to try a MK5 throttle as they were improved, but don't have the coolant inputs, so I'll just join the two hoses together.
There are no fault codes in my case, which is odd because if the ECU is trying to open the throttle X percent to maintain a cold idle, but doesn't get there, I'd expect that to show up in VAG-COM, but nope!