Guys I have quite a bit of time on an OS 46 FX with a stock muffler and the Tower muffler. Flying a 4 1/2 lb Sig something extra with the stock muffler,11.5x4 APC prop. This combo had plenty of power to hover and climb out with authority. I got a U-Can Do 46 and installed the engine out of the something extra. Put a Tower muffler with the same prop and it gained 1800 RPM. Also the midrange is much smoother. Throttle response is almost electric like. As you guys know a UCANDO is a large airplane for a .46 and it fly awesome with this set up. The guys in my club can't believe its not a .50 SX. Anyway short version the Tower muffler is a great buy and in my experience a full tuned pipe would be the only thing that would out perform it. Not in price or weight but slight bit of top end. The fellow with the Thunder tiger. The reason an OS muffler doesn't work on the TT is they are not port matched at all. Where the stock TT muffler is matched to the engine. Just because they bolt on doesn't mean it will work as good. Jason