94 Cutlass Ciera 3.1 - Hesitation after cold start

Hi,

I have a practical "do's and dont's" question. My '94 Cutlass Ciera 3.1 has the following problem:
After a cold start, it will run at raised rpm. No problem so far. But, after a minute or so, when the rpm wants to drop to normal, the engine will sputter for few seconds. Then, apparently the ECU notices something goes wrong and races the engine to a higher rpm again to try and compensate.
Sometimes it will stall, but most of the time it will pull through.
Sometimes this all happens a second time a few seconds later, but less noticeable.
It happens standing still either in N or D.
After that, it will run great with no problems.

I read in a previous thread to clean out the Idle Air Control. I took off the throttle body and removed said item. Indeed, there was a certain amount of carbon deposit there inside throttle body, and on the metal valve pin of the idle air control. I cleaned it off.

As expected: No improvement; still the exact same problem.

Question:
1. The idle air control motor/activator seems to be a closed assembly. Can it be dirty inside? If so: How to clean it?

2. Someone also suggested the EGR valve might be dirty. Any step-by-step directions for me to show what it looks like, where it is, what to do and especially what not to do?
--> I don't want this to end up like one of those repairs with me paying the dealer a lot of money for him to repair the stuff I damaged trying to fix it myself :-D

Thanks for the help!
Wekke