Originally Posted by XwChriswX

They are headers that bolt both onto the engine, and then straight on to a 'Cat Back Exhaust'. Also known as a 'Cat Delete', since they take up the space the Cat or HFC would go as well due to them being longer than normal aftermarket (say Stillen) headers. They give you the cleanest path for the gasses to flow from engine to rear bumper. That = when you floor it.

I can say first hand from the experience with my tC. When I put on the cat delete header, you could Instantly tell with the butt + seat test. And as for sound, it REALLY opens up your exhaust. It will come with alot of rasp, so you wanna have some decent resonators to minimize that. (My tC has 2 now.)

But you can definately see a difference in the driving experience, and based on my previous experience alone, I would highly reccomend them. It isn't legal everywhere, so if you get emission tested, make sure to keep your stockers. Although installation/removal can be time consuming without the proper tools. But not impossible.