[Wgesnerjr]

We have not discussed this, but sounds entirely plausible. With the timing of the issue, I thought it could be something along these lines. One thing that keeps me thinking otherwise is that only one side of the engine runs rich. Would a bad program for the ASE cause a rich condition on one side of the engine?

The other thing is that my set up is very stock. I did not ask LT1swap to do any tuning except VATS, delete rear O2 and Speedo calibration. so I wonder if he would have touched the ASE anyway? And for what reason.

The only parts I thought would affect just one side of the engine would be injectors, O2, or the program in the PCM. Things like MAF, vacuum leaks, PCV or EVAP I have been shying away from as they would affect BOTH sides of engine.