I have an YS63 with about 2 gallons on it. I was running it with an Enya 3 plug and it did not have a good idle but midrange and highend as well as transistion were good. Today I went flying and my plug was dead so I changed it with a new OS F I had in my flying box. It has changed completely. Idle is very good and will idle for ever. The high end is also good and I can adjust it as lean or as rich as I want, but I have a problem in my midrange. It is doing a terrible sound that I think is detonation that disappears if I am able to go to full throtle. Adjusting the high end needle has no effect. It seams that the plug is hotter and needs to run richer. How can I adjust it to make the midrange richer?