Thanks guys, I have started to read though the whole thread, a lot of pages to read. I believe I might have a Pitts muffler running around somewhere, is there any performance difference when using a Pitts style muffler? I had it on a 55ax in a Funtana X50 but later switched to a Tower 46 muffler. I could hardly believe the difference, gained 900 rpms same fuel and prop by going to that $15 muffler.... Anyway, I will go ahead and get to reading, I am looking forward to my first foray into gas engines.