I have about the same results. I run 20% Cool Power Fuel. 2 head shims on APC 18.1 x 10 prop. RPM 7800 to 8000. Currently flying two Focus II 2 meter aircrafts. Tuned pipe on one is the Aeroslave and the other EDS from central hobbies. Muller 3/4" headers. The plane with the EDS tuned pipe has the Webra 12mm carb. The mid range seams to be better with this carb. I plan on changing the other one to the 12mm carb. I have installed stainless steal rear bearings which last much longer than the Webra orignal or ceramic.