1994 Pontiac Sunbird

Hello, I keep having this problem with my car. The car seems to run fine until its fully warmed up and the temp gauge gets to where its suppose to be. Which means to me the car is idling higher when its cold. The problem is when im in drive or reverse at a stand still or barely moving the starts idling erratic and eventually dies or sometimes it just idles erratically until I get going again and then its fine. Ive noticed the oil and battery gaues fluxuate when this is going on. So alot of stoppin and starting in city driving it is dying on me.I have replaced the fuel filter, put new plugs and wires in, checked the map sensor and have put a few different fuel system cleaners in i. But still the problem remains. Also had it in the shop today and they said there was a idle code in there which they reset and said it didnt come back when they turned it off and restarted it again. They said they checked for vacuum leaks and didnt see anything abnormal. Ive done some research on hear and keep hearing it could possibly be a intake manifold gasket, if so would I need both the top and bottom gaskets? Your thought appreciated. Thanks