So would partially blocking one of the exhaust tubes on the pitts muffler help or hurt this situation? I partially blocked one of the tubes on my gms 40 and now I have great fuel line pressure, idles great and rips up to full speed like a speeding bullet. Not sure if this causes a hardship on the motor though. Motor seems to be doing fine. This was all caused by Tower sending me a .47 pitts for my .40 motor. The .40 pitts has smaller exhaust tubes (3/8" od) and the .47 pitts hast 7/16" od. Caused motor to lose power at high rpms due to lack of fuel.