I've bought several for .25's & .36's that were used at very good prices and currently have two more for a .46 on order from Quantum...I paid $29 each for them. I like them because they are one-piece, look nice, are streamlined and light. It appears that drilling the tailpipe out will improve the top end and result in no side effects.

Personally, I think the Tower .46 muffler is over-rated as I have seen the same RPM's out of a TT PRO .46 muffler with the baffle removed and the tailpipe bored-out. The TT muffler is also quieter and smaller...possibly lighter, too.

If I want even more performance I simply make a mousse can pipe...those DO work quite well and are typically lighter than a stock muffler when built the way I build them. I'm going to post a thread on my method when I get the header for one I'm going to make for a TT GP .15. The thread will have pictures of each step of construction. It ends up making a nice looking, light muffler that gets a LOT more out of an engine than a stock muffler will...even with the baffle removed and tailpipe bored-out.