RE: Jett SS/LX Muffler - Gold
If you have a gold LX muffler.... too much prop.
What prop are you using?
That muffler really needs to hit 17,000 rpm ground peak to begin to work well.
Minimum ground peak target would be about 16,500. Prop selection should has to exceed 16,500 by a good margin. Then back off 600-700 rpm from the peak for flight.