Ever wondered how those zokushas have that sharp high pitch when revving their engines like this?

The principle is very simple: normal exhausts have mufflers which silence all sounds whil most aftermarket exhausts will silence all high tones to give that deep bass sound. To get the high note like the zokushas you need to do the reverse:

How to create a bosozoku style high pitch muffler

First take an exhaust with the widest pipe (to lose least sound as possible).
Read on for more pictures and info...