Interesting that you got your best power running that lean, if your pump gas is truely the ethanol blended stuff we have here in PA. Most of the country runs (May contain up to 10% ethanol) pump gas. Nobody is sure of the mix, but it's not 100% gasoline. 100% gasoline likes around 12.6-13.2 for Max power WOT air fuel ratio and 14.7 stoich.

E10 (10% ethanol) blend likes 14.1 for stoich and (estimated) 12.2-12.8 air fuel ratio for max power WOT.

Maybe your blend doesn't have too much ethanol.

I'm just gathering this kind of info, to better tune my pump gas car with my LM-1 monitor.

Thanks,
Larry