I tried his prop, his muffler, his fuel, and nothing, I even have another Super 80 at home, one that I got completely rebuilded from RC Showcase and I started it and the RPMs on this one are the same as my other engine 5900! So my friends engine is special or something, The only thing I have to try is his ignition, he has one of the newest ones which I know they have been modified and improved! Maybe that could be doing it!!!!!!!!!