I have a 402 LS2 that is local built and ran fine for a short time. After getting some chassis work it now brakes up under load and seems to be on a 2-step around 4500rpm and up. I have changed the plugs, wires, 02's, coils, computer, tried 4 different MAF's, checked and redid the ground wires and the problem is still there. When data logging the car the only problem I see is the MAF does not send voltage to the PCM only pounds per min and the pass side 02 dips real bad. I checked the plugs after a pull and they look fine. Anyone else have this problem before?

 

This may help, find a vacuum port and get a vacuum reading. The engine life and diagnostics can be found in the vacuum reading. 18-22KPA normal, anything below that is not good so good.