What you are saying sounds just like I had on a .46 engine whith a Pitts muffler. I plugged the outlets, played with needle settings, and it would run great at or above about 1/3 or above. I had almost given up until I installed an oscillating pump and all was well in the world. It sounds like the muffler is not generating enough back pressure to supply the fuel at idle. Have you tried to close one out let all of the way??? Not sure if the little pump I had would even keep up with your engine at idle.


Dru.