I'll let Scott confirm, but I think the O2 sensors are "out of the loop" so to say under WOT. They are only used for closed-loop optimization. What I don't know is whether the closed-loop fuel adjustments (long term fuel trims) affect open-loop operation at all. My impression and limited testing is no.

The graphs posted, to my limited knowledge, do look like the AFRs are too rich. I actually have the same problem on my 986 (stock OE program). From what I have gathered, dropping from stoichiometric down to around 13:1 is what to expect for WOT, 12:1 is even OK (but no extra power), and below that loses power. Mine is as low as 11:1 or 10:1. There was a tuner (Upsolute) that allegedly would tailor your fuel maps if you provided them with AFR graphs. The company looks sort of defunct, though. I also had GIAC on mine. The AFRs were a little leaner than the stock program.

It would be great if Scott can comment on the whether the LTFTs (closed loop) have any impact on WOT fuel maps and if he could do any AFR adjustments. I'm sure Scott is a busy guy and provides a decent "generic" program. I would be interested, for example, if there was a "premium" programming option where, for some reasonable surcharge, he could adjust the fuel trims. I'm sure Scott knows where the AFRs should be on these cars and maybe this can be offered as part of the generic package or offered as a premium option.