Does anybody with experience know what cutouts do to the A/F mixture if you are running a stock exhaust w/ all O2 sensors? It just seems to me it would be better for the engine to have a nice high-flowing system and tune the engine to the system rather than run 1/2 through a choking exhaust and 1/2 through open pipes and be confusing the PCM all the time - but I'm wondering if that's really true?
If they are placed after the post cat (downstream) O2 sensor they will have NO affect on A/F.
A freer flowing exhaust system will allow the engine to rev quicker, I.E. inhaling incoming air quicker which then uses the MAF to correct for the freer flow in conjunction with the proper fuel trims being determined by the switching in the O2 sensors. So no affect. There's more to it than this, those are just the main players that contribute.
Really anything after that second O2 sensor is nothing more than noise abatement.