I have experimented with 91 octane gas in all my two strokes and found that the octane doesn't do much to improve power in most situations but it does improve idle slightly and the engine runs noticeably smoother. I now, run 91 octane in all my two stroke engines, even my outboard, and I plan to run 91 octane in my conversions. I have not tried 100LL avgas in my conversions, but I will as soon as I can get my hands on some.