The computer uses the MAF, BAP, ECT and ACT sensors at WOT. The O2 sensors are active but only for the purpose of detecting a dangerously lean condition. They aren't used for adjusting the air/fuel ratio since the computer is trying to maintain a richer a/f ratio than the O2 sensors can measure.
The fuel map is based on a separate lookup table for WOT, but those numbers are adjusted according to numbers calculated during closed-loop control.
When the computer is reset, it will use some preprogrammed numbers based on RPMs and the amount of air being measured. It will use feedback from the O2 sensors to adjust those numbers. It stores these numbers in an adaptive strategey table in terms of an adjustment factor. If more fuel is needed, it's greater than 1. If less fuel is needed it's less than 1. That's basically close-loop mode. At WOT (open-loop control), those adjustment factors are multiplied by what the computer looks up.
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351W 89 Mustang GT Convertible