Can someone confirm for me what I would see if logging with exhaust leaks before the heated O2 sensors?
Will the PCM pull fuel? Would this then contribute to a lean condition, thereby causing the PCM to pull timing, especially under load or WOT?
Thanks,
Rich

 

It will add fuel because the car will pull in excess air making the O2s see this air and think your lean, ergo the car will run rich compensating for this.