I believe when you use the o/r pipe it will cause your car to run actually richer. With my cams and o/r pipe my car runs really rich. I need to get a tune. This will not hurt your car. Anything is better then detonation
The O2 sims are just there to lie to the computer that the cats are supposely still there. The back 2 O2 sensors are really of no importance. There job is to let the computer know when the cats are missing!!! or not working correctly. When that happens the check engine will turn on. The sims correct this from happening. I believe they will have nothing to do with the mixture control. That is what the front O2 senors are for.