Around here, BP/Amoco only has 91 octane. Tesoro, I have found to be much better gas (at least in my WRX). It is rated 92 octane, but it seemed to run much more timing than other 92 octane brands (at least around here). I have not run anything but Tesoro in my STi, except while traveling. Maybe I should try the "lower octane" 91 Amoco rather than the "tried and trues" 92 Tesoro??
What about higher octane ethynol blends?