HKS and APEX AFC's?

I've been doing more than my share of ECU diag lately for both imports and domestics, and in the process have beaten the open-loop/closed-loop ECU scenarios to death. After first noticing some less-than-optimal behavior at WOT (running very rich) on a Camaro SS I've been working on, I toyed around with my 'teg to see how rich it's been running at WOT. It seems to have next-to-no power difference between 80-90% throttle and WOT, which gives me the impression that there's some more power to extract out of that top-end by tuning the A/F mixture.

So... after some reading around, I found the HKS AFC products... An ad I saw claimed a real-world 5-9% (dynoed) gain when working on base-model 1.6l civics. Those numbers sound really high to me, so I was wondering if anyone has installed and tuned an AFC from either HKS or APEX in their Integra? Did it make any spectacular difference?