I could be wasting my time and money, but I have had good luck using regular grade (87 octane) pump gas (Ethanol added here where I live), and a splash of octane boost (whatever's on sale) along with synthetic 2-stroke oil. I also add a splash of diesel.
My engine is warmed up a bit, and I have shaved the head to raise compression, and only rarely do I hear pre-ignition (ping), and only then on wide open throttle, and maybe pulling uphill. I do have a Jaguar CDI, which is supposed to retard ignition timing at high rpm though.
I used to use premium gas, but found that with multi-grade gas pumps, you are generally getting a hose full (3/4 of a gallon) of whatever the pump last dispensed (usually 87 octane) anyway, and when you're only buying a small quantity of gas, this is significant. - - I also feel that because of the higher cost, and slower sales of the premium gas, it is far more likely to be stale, due to sitting in storage longer than the regular grade.
I have also had comments from friends that their bikes run better on my gas.
- - Just my thoughts.