from what ive been told, octane serves to prevent detonation. running high octane fuel alone would be contrary to your performance needs. using higher octane fuel in conjunction with more boost or a bump in compression would help extract more power. i would think then using a fuel with an octane rating that keeps you on the borderline of detonating would yield the most power.
im going drag racing next weekend, and i was thinking about getting the most power i could with my wrx as is. a stock wrx needs at least 91, right? you cant get 91 around here, i think 92 or 93 is the lowest. if i ran half a tank of 89 and half a tank of 93 i could get 91 octane. (89+93/2=91) im assuming this should be able to provide the most power for my situation, and the same basic idea should apply to you.
are there any chemists onboard able to explain in any more detail?