I recently had a new engine (Jasper) installed after an accident in an '05 GT. While there, I had nex OBX headers installed too. I did have a JLT intake, but after some code troubles I returned it to all stock, except for LT headers. Right now, I have the stock tune installed and have the following codes:

P104/0161 - O2 Heater Circuit Bank 1 and 2
P0600 - Serial Connection Link
P1000 - OBD System Readiness
P2105 - Throttle Actuator Control System Force
P2270/2272 - Sensor Stuck 1 and 2 - Lean
U0300 - Unknown

This only happens when it starts from cold. If I drive around some, then clear the codes, restart, and drive around the codes do not reappear. But it does take a little longer to start the engine. It cranks for a couple of extra seconds compared to the original engine.

I did try to install the 93 Performance Tune from Diablo and I get a "Engine Failsafe" mode and I can't even start the car.

Could this be from the headers? As I read back over this, I also wonder if I need to tighten the MAF after swapping back to the oringial intake. But any other thoughts that I should check would be helpful.

 

LT headers need a tune for O2 codes, but not the codes you are getting. Sounds like maybe the O2 connectors are swapped (driver side plugged into the passenger side header, visa versa).

Those other codes...I dunno. Question for the engine installer.