I bought the engine without the muffler and use the Bisson Pitts muffler. Only one issue though, you have to close off one of the exhaust tubes to get the engine to run right. The Bisson Pitts does not produce enough back-pressure for this engine or the 1.20. I just crimped one pipe at the box with a pair of vise grips leaving a very small opening for any fuel to run out and the engines run great!! Both pipes are still there and look good, where they show. Found the tip in an old RC Universe Review on the 1.20. The key is that you should never use a muffler with a larger opening then the stock muffler. If you do you will usually find that the mixture screws have little or no effect. Don't know if that's why you're looking to trade but hope it helps.

Al Lewis, USAF ret'd