New motor issues.. Need Help!!!!

[twright]

I have a 1995 Yukon that I have just recently changed the motor in. I keep having the same issue no matter what I try. The Yukon keeps missing out and is down on power on acceleration. It will actually run great for about 30 minutes and then the same issue starts up again. We have tried: Replaced the fuel pump and filter, replaced the TPS sensor, replaced air control valve, adjusted the valves, checked for faulty plug wires, replaced sensor in the distributor, New plugs, and have replaced a broken vacuum line. It seems that when we tried one fix it would run fine for about 30 minutes but then the same issue comes right back. Any help or advise on this issue would be greatly appreciated!

 

[dddsnapon69]

does it just start missing, or actually stall and not restart.