I am just trying to figure out what it is called and where I can find one. It is a vlave that is usually installed just after your downpipe before your cat. It can have either a mechanical or automatic control to open a valve and dump your exhaust off like an open downpipe. I feel stupid but I found them before but I can seem to find anything on it on the internet again. please help me! Thanx

 

they're usually referred to as "exhaust cutouts" search the usual places. google, jegs, summit, ebay

 

I just ordered the one off of dmhperformance.com. I've been reading a lot of reviews, and people seem to be the most happy with it. Good warranty too.