here is a link to an exhaust system that lets you have the power of an exhaust system without mufflers or cats at the touch of a button, then when emissions time comes around can be closed to pass

http://www.quicktimeperformance.com/qtec.htm

I have finnally provided something usefull I believe

 

interesting...

 

I've heard of them being used on trucks but never imports.

 

i'm assuming that this would not be cool in states where the emissions inspection includes a visual inspection of the emissions equipment.

 

that would cause too big of a loss in backpressure to of any use to me... but its a nice idea for people with turbos.

 

BMW's have em stock (built in), or so I've heard

EDIT: I also heard that the driver in the BMW cant directly control it... when u accelerate hard, it opens. But, if ur just cruising, it's closed.