G94 Grand Am Stuttering and stalling

[NicelowZ]

Hi! I am new to this board and new to Pontiacs. Anyway I bought a 94 Pontiac Grand AM GT with the 3.1 V-6 and it had a broken cam. I just replaced the engine this week and got it running. When you start the car it will run fine for about 1-2 minutes and stall out. Start it back up and it will run like crap for about 30 seconds and clear up. It will run again for another 1-2 minutes and start to stall again. If I just tap the gas when it starts to stall it will run fine again for a few minutes. The car also hessitates when taking off. One more thing the car will not go past 4200 RPMS. It acts like a rev limiter but I thought that did not come in untill redline? Things I have replaced,

Plugs,
TPS,
IAC,
Engine,
Checked all vacuum lines.

Any thoughts? Thanks alot!! Paul