David,
You're welcome to drop in to Lockhart, TX any time and take a look at my p-port 3-rotor Lancair ES. It reliably produces loads of horsepower, while cruising at over 200 mph on about 11.5 gph. And yes, it is loud. Any "quiet" mufflers I've tried have increased EGT's while reducing top speed, or didn't last long enough to find out how well it worked. I'm still running a "DNA" muffler (made in Canada).
Mark S.