For me, the tower muffler made about 1500 RPM difference and the engine has more torque throughout the range. It's a lot louder than the stock muffler with baffle and noticeably louder than stock muffler with baffle removed. On the other hand, I've heard the full-size tuned pipes run and it's nothing like the noise those make. I bought it on advise from RCU. It's by far the best bang-for-buck performance you can buy for a 40-46 engine. (you can make a cheaper one, but can't buy one). Clean the threads with acetone and use loctite on the through-the-muffler screw or you'll lose most of the muffler.

I, too, really liked the low noise level of the stock muffler with baffle. But the extra punch was worth it. The plane holds knife-edge much better with the tower muffler. Before, it was tough to keep the nose up.

I had an old 1978 K&B 61 RC with perry pump. My gosh, that thing was so loud it was painful. But you talk about some power! I could hardly stand to be close enough to it to tune the needle. I never could get it to transition, and it was a making my wife really hate the hobby just breaking it in, so I sold it.