In wraparound Pitts mufflers, I've had the Peacemaker (from J&A) in my QQ Yak as well as the Slimline in my WH Edge. Both perform fine and are well made. The Slimline has more cubic inch volume and as a result is a bit quieter. I purchased the J&A since it was more compact and I'd need less cutout in the QQ cowl to fit it. Bisson, JTec RC make their own as well. TroyBuilt models offers their own TBM mufflers which I'm guessing might be imported...don't know for sure. Bisson seem to be a little thinner/lighter and they are good people. Slimline are widely available. J'Tec will happily customize a muffler for your application if needed and are also great to work with. Some include a strap to support the end of the muffler that's between the engine and firewall. The strap is a good idea.

some links for you:

http://www.jtecrc.com/wraparoundpittsstylemufflers.htm
http://www.troybuiltmodels.com/Mufflers.htm#IN-COWL
http://www.slimlineproducts.com/onli...iant_scale.htm
http://www.bissonmufflers.com/en/muf...mageField.y=14

Have fun!