idle not so good when engine is warm

Hi there. I have a 1988 firebird formula, manual 5 speed tranny and a 305 h.o.
TBI injected engine. When it starts from cold, the idle will go to 2500 rpm and stay that way for quite a while(like choke sticking). Then will run ok but has a rough idle when warm and at a stop...it won't really quit but seems to not run on all 8 cylinders and rpm's drops below 450 then oscilates to 900 then back down again...engine will then hesitate when i give it gas. The engine temperature is descent but this only happens when engine is warmed up. I did change the IAC valve and I also changed the throttle body gasket because I detected a air leak(using the old carb cleaner trick). I am getting bad gas milage too.I am now a little stumped and wondering if the EGR valve is bad or maybe the O2 sensor...What do you think!!!

Does sound like another vacuum leak......

Check for codes? don't need a scan tool or code reader....

Since it idles poorly when warm, does it improve if you spray carb cleaner directly into throttle body?

Thanx for the reply! I did a code check on the ECM via the jumper cable and i do get a stored code 24 but the light never comes on... and yes the engine soon light is not burnt!!! I did not shoot carb cleaner directly in the butterflies... what should I expect? idle up? idle down?

If it smooths out, it's running lean.....could be injector(s), vac leak, fuel pressure, etc.

If it bogs down, it's running too rich....

Check that MAP sensor.....

Will check asap... one thing i was wandering about: code 24 is supposed to be the vss sensor but on my v8 vin E it is the map sensor... why? Anyway thank you very much Tech your input is greatly apreciated. Car is now stored for winter, but I can work on it a bit if not to cold or snowy outside...When I figure it out , I will reply...thanx again man.