I second (or is it third?) the TT. I've had both. No comparison. I switched from TH to TT when I started having problems with my TH dying after takeoff. No one at field could figure it out. Swapped out the mufflers and have never looked back. In my 40 Uproar I'd get unlimited vertical, and I'm not convinced the muffler had that much to do with it. I put the same engine with a Bison muffler in a much heavier GP RV-4 kit. With a Zinger 11x6 it pulls the RV-4 all over the sky. And it is a super smooth idler. A number of times folks have thought it deadsticked when I pulled it back to idle in flight, only to be pleasantly surprised to hear it come to life again with an advance of the throttle.