ORIGINAL: ChuckW

It really depends on the situation and the engine.

For a side mounted 2-stroke inside a cowl, a Pitts muffler is a great way to go. There are also cases when the engine is inverted and an inverted Pitts is helpful.

If a 2-stroke is mounted upright though there is rarely a reason to use anything but the stock muffler. I have used the Macs mufflers to replace broken stock mufflers on Super Tigres however and they do work great.

Of course there may be applications such as racing or other things where you will want to experiment with different mufflers or tuned pipes, possibly even building your own set up.

On 4-strokes, I have used only stock mufflers so far but I am thinking about a different setup for a Mustang that I'm currently putting together.

Basically everything has its time and place.