I just finished putting the car back together after a 3 month project of rebuilding the trans and putting in a new engine. It started right up and after letting it idle for 30 to let the smoke from the anti-seize burn off, I took it out for a little drive.
After 20 miles of driving, the car would sometimes stutter and buck when I would give it gas (think of the 3000RPM hesitation only 10X worse) At the same time, the exhaust would be backfiring and the engine would sound as if it was running on one rotor. I could be cruising along in 3rd gear at 2000RPM and it would start doing it, I'd downshift to 2nd and it would continue. And then just as fast as it would start doing it, it would stop. Then the car would run fine for a few miles and start acting up again.
The whole time I was driving, I was trying not to make any boost to help break in the new engine. So when I say I'd give it gas, it's not WOT and the turbos spooled up. It's really just a small change in the throttle.

Other information if it helps - The car is totally stock. The ECU has been unplugged for 3 months now and someone said that it would revert back to a new engine setting.

Any help would be appreciated. Or maybe even a starting point on what you think it is.

 

im not joking mate,,,that sounds like limp mode,,,,try do an ecu code check... i bet you cant make any boost at all

 

Something I totally forgot about. I'll pull the codes and find out what the computer sees. Thanks

 

TPS- check it work it fix it clamp it and go