We did some tests on optimax in the bikes and found it lost around 2bhp per 100 over stock unleaded. My 18 runs very well on stock unleaded but runs like a bag on high ron stuff.
I did some back to back runs on the 21 with unleaded and avgas and when jetted for avgas picked up just over 1bhp. Not a real improvement, i got better results playing with boost bottles.
_________________
If I have to take the carbs off once more...