ive also read mr12 can be a little erratic in high heat, but you dont want any detonation period. i dont think u even have a choice with ur motor, mr12 only, especially in this heat. even the lightest detonation, the kind we cant sense, destroys hp. if i ever have the chance to finish my bike, gotta try 12 after all ive read. mr9 is great fuel, designed for stk.comp. sportbikes. 12 designed for higher comp. modified motors as yours, i wouldnt be surprised if this fuel isnt tempermental, when run with the compression it was designed for, as in your motor. let us know what u decide and how it turns out. good racing toney.