I will caution you that plug reading with Ethanol or Methanol is more difficult because it does burn so clean on the plugs.... We finally bought an air fuel monitor.... We also do our "spring tune-up" on a chassis dyno that has a mixture analyzer...after a couple pulls, we know where we're at on the jetting, plugs, timing, etc.....

Some say it's a lot of hassle to go through, but IMO the difference in price from our E-90 to race gas with a comparable octane more then justifies it!!!!