I am fortunate enough to live near a 76 station that has 100 octane race gas and I use it usually mix it half/half with premium, although many times just run it straight. The 100 is not cheap, but I am running 10.9:1 cr and once I started using the 100, I was able to go back to optimal timing. There are websites that you can use to locate high octane fuel suppliers near you, like Sunoco or 76.
Good luck!
