no sweat..
AV GAS is usually around 100 octance..
Race Fuel can be different between brands..Sunoco Fuel is 112 octane, Renegade is like 110 octane..
like the others said above..if your running a stock motor then 91 is fine..if your running NOS then you NEED to bump your octance for sure..to prevent detonation...
for example..i have a 10.8/gal fuel tank on my 900...if i ran 8gallons of 91 octane..with 20% (2 gallons) 110 race fuel, i will have about 94 octane combined and that is good to use with NOS..AV GAS will need more like 50/50 AVGAS and 91 octane..
make sense..