[CSG Mike]

Originally Posted by Gords_zenith

I'm not so sure I would agree with your statement. 100 octane will certainly resist detonation caused from igniting timing being to far advanced, and super lean conditions, better than say 91/93/94 can. Remember it takes more advance, the greater the octane. My guess, based on reading some things here, is that the super lean condition(20:1) that presents itself when the throttle goes closed, plus the super advanced timing(39 degrees is what ive seen)at that very moment seem to contribute to the detonation at throttle tip in. So in the end, I truly think running race gas or something equivalent may prevent the detonation until Subaru releases a proper ecu update to correct this. Or just shift slower in the mean time?

It is indeed more resistant, but it's not THAT much more resistant. Otherwise, you'd see more gains on a NA engine tuned for high octane with ultra aggressive timing.