>>> Which do you guys prefer, the stock muffler, a mac's muffler, or a pitts? I just recieved my engine today, and can't decide which muffler to use. I installed the engine on a H9 Pawnee >>>

Scott, read post #391 by flatspin. He lost a ton of rpm's by going to the mac's black one piece muffler. This baffles me since that muffler is the extra volume one made especially for the 60NX, 55AX, etc.

Flatspin, you are sure your mac's muffler is not the one for the .46, right? It will bolt right to these larger engines also but is too small.