I have a Great Planes .40 size Ultimate Biplane with a Sullivan slant style fuel tank and an OS 46 FX engine with a Bisson Pitts Muffler attached to it. I seem to have a problem somewhere in my setup on my plane because for some reason when I go full throttle it almost always shuts off completely. It doesn't sputter or anything of that nature. Just dead. I've tried putting on a new OS 46 FX to see if it was a problem with the engine but it did exactly the same. I have the new engine on a H9 US40 and it's doing great. I've replace all of the fuel lines and even went away from the dubro kwik fueler and went with a 3rd line for filling and that hasn't helped any at all. I've even had the most respected engine guy at my field look at it and he is completely stumped. Has anyone out there had any similar problems? More importantly, does anyone have a good answer to fix this problem?