Diagnostic trouble - 3.4L stalls when started warm

My Alero V6 starts fine when cold and runs ok, but often when I start it warm it sputters and stalls out unless I rev the engine. Even then it idles rough. I was fully convinced that there was an engine vacuum leak causing this. Last night I hooked up my new vacuum gauge (with engine warm) and it read 18" steady at idle, dropped to zero at open throttle, jumped to 23" and back to 18" at release. No decrease in vacuum at steady 2000rmp. Basically passed all the tests (I did not do cranking vacuum test). Is there something I'm missing? Any other test I can do or possible problem causing my symptoms? The only code right now is P0442 small evap leak. Thanks for any input.

The engine vacuum readings look good.

Have you tried cleaning the throttle body especially the IAC (idle air controller) and seat where it mounts to the TB. When was the last basic tuneup?

The engine vacuum readings look good.

Have you tried cleaning the throttle body especially the IAC (idle air controller) and seat where it mounts to the TB. When was the last basic tuneup?

Actually, that is exactly what I did yesterday, using info from this site. There were a lot of carbon deposits in there. I have not driven enough to know if it helped, but I am sure it did not hurt. I've been doing tuneup stuff a little at a time for the past couple weeks (new PCV valve and air filter.) I have spark plugs to put in too.