Jumping in to clear the "air". When Mike's Z left California it was tuned for high 10s and low 11s. His environment (altitude, pressure, humidity) will attribute to changes in the tune. With that being said 10.5 under WOT on a high compression engine not intended for boost is perfectly safe. On the other hand if your idling and cruising at 10.5:1 AFRs then there is cause for concern!
Another thing to remember is air is 500x times lighter than fuel so when you first hit the throttle you'll see transient fueling enriching quite a bit to account for the huge rush of air entering the cylinders. You may see it dip down but otherwise it will stabilize.
Brand new forced inducted vehicles, for example GTRs, EVO Xs, etc., have a nice soot build up on their tips and the bumpers get "coated" black even after a minor amount of miles. This is with them having two sets of cats on them still. I think Mike's post was taking way out of context and the way it was written makes it sound like something is wrong.
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