someone please help!

ok, i have a 92 gtp with a 3.4 dohc. the car is acting horrible. it accelerates very slowly at low rpms (up until about 3000). when i slow down to a stop, the cars idle with jump but never go above 1400. when i try to start moving again, i hit the gas and the car will rev up to about 1800rpms and then die. then when i try and start it, it starts very rough. these problems only seem to happen after the car is warm. the pcv valve is new, spark plugs are new, uim and lim gaskets are new, fuel filter and fuel pressure regulator are new, and the air filter is new. I brought the car to tires plus and they said that the car is getting proper spark and the fuel pump and injectors are working fine. but they gave up and couldnt figure out what was wrong. I dont know what else to look for to figure it out. any suggestions or advise would be greatly appreciated. if no one on here knows than i will just take it to a dealer. (and i will try the maf test from a previous post tonight.) thanks for any help.

There is a good chance the timing belt jumped a tooth. How long have you owned the car, and how many miles on the belt? The change interval is 60k, so if you have more than that on yours, I'd start there.