i am using powermaster 10% for now. I might use somthing else when i'm ready for it. I think you are right Left, he prolly would have told me somthing about it. I just don't understand how unburned fuel could turn black if there is an exhaust leak.

While he was flying it, I asked him if he has flown this plane before and he told me that he has trained at least 25 people with this exact plane. He also stated that this particular plane flies much better and has a stronger engine than any other alpha 40 he has flown.
I think it might be because I exchanged the three blade prop with a 10x7 wooden master airscrew. Maybe this makes a difference???

Joe