[mack]

This article in this site is interesting:

The next myth has to do with performance mufflers. Performance mufflers are not just for kids, they can improve many aspects of a car. These include power and the gas mileage a car gets. By letting an engine work easier with a larger exhaust pipe and performance muffler, overall performance is acquired. Decreased engine temperatures are also a side benefit. Of course there is also a louder sound as well.
http://www.autosupportforum.com/gene...omotive-myths/

What it seems to say is that the loud mufflers that teens use in their cars do have a function. They improve mileage and engine performance. I used to think those mufflers were installed just to impress people.