08 Mustang GT CMCV Delete 91 octane tune ? to lean it or not

[mmorningstar]

DETAILS:
U7145-9R03 crom
Steeda IMRC Tune 91octane(cmcv delete)
90mm steeda MAF
Saleen CMCV deletes
Ford Racing X
SSS Axle Backs

I live in PA and run 93 octane, my exhaust is RICH, more than it should be, collection of black on the tails all the time, do I need to lean out the global by 2% or so?

[Vas@Diablosport]

I really couldn't recommend adjusting your fueling without knowing what your AFR is like. I'd suggest getting a wideband o2, or dyno time.

[mmorningstar]

where is the preferred placement for a wideband O2 on the 08 Mustang GT, is there a specfic cylinder that is considered the "leanest"? Example, on my 04 WRX I had my EGT on the front left Cylinder as that was considered the "leanest"....