I'm running 12.25:1 compression on my gsr and I can definate feel the effects of octane/compression...
On hot summer days I can't go with anything less than 94octane or else I'll here some pinging... but in the colder months I can use 92octane without a problem, because as the temp. drops so does the octane rating that I need

I've tried 92 with booster, but it not as good as 94(the problem is I have to drive 45+ min to get it... if It wasn't so far I'd use it all the time)

if I use 100 octane I can bring up my timing to stock 16-18degrees, but right now I'm at 13-14degrees just to run 92

GSR's have a knock sensor to cut back performace if the octane is too low..so if you ran 87 it wouldn't kill the engine, I hear that you'll lose about 15% of the power, the ecu probably cuts the timing back..