I have a turbocharged mustang and I have done alot of research on the "what fuel to use" subject. From what ive seen it is best to use the lowest octane you can without getting any pre-ignition.
In newer cars too low of octane will actually take away a LOT of power because they have knock sensors that retard timing and richen the mixture IF and when it senses knock (pre-ignition). But these bikes dont.
The lower octane burns faster, easier, hotter and more completley. There for having better emissions and less carbon build up. That is why engines with really high compression or forced induction can not use it. It will ignite just from the exreme heat from the high cylinder pressures, before it is supposed to. (pre-ignition)
I dont want to step on any toes but if you put race gas in your stock savage and think it is faster its probably just the smell of it getting to your head.