I have checked all lines and have installed small zipties on fule line. I have a bisson pits muffler that I have peened the ends of the 2 exhaust tubes to increase back pressure (just slightly larger opening areas thatn original muffler). The engine runs well on the ground but in the air it has deadsticked twice. I have a large fuel line with large brass tube in stopper and large clunk. It appears to me to have good fuel delivery at 1/4 to full throttle but at idle and just over the pressure just doesn't seem to be there to push fuel to carb. I haven't tried holding the plane vertical yet but will try that as soon as I can talk my wife into controling radio.