I'm using Byrons Gen2 30% / 11%. It was rather hot and humid. I also had 1 new plug that was bad out of the pack. The engine would die as soon as I pulled the ignitor off. New plug fixed it. I cant see using any othe pipe at this point. It really made it sing. But with a 15t it was wound out in like 20 ft LOL. The head looks massive but it is really lightened a bunch.