Sound and performance are two opposites.

More performance = more sound.

Some cheap things you could do would be to try taking out the baffle of the stock muffler.

You could also get a Tower 46 muffler for $13.99. It will give you a few rpm too.

A tuned pipe will be around $65 by the time your done with it. They are good only for speed racing type planes and are a waste of money for 3D types. They are also difficult to get set up properly and are not just a bolt on device. Just to put one on your engine is nothing but a ego trip and a waste of money.

The are some other bolt on type mufflers like the PSP and the Jett.

Enjoy

Jim