Matt200

Any tips? Helpful things so I don't mess up would be nice.

And I don't care if it's illegal, so don't bring that up.

Katman

It may sound 'odd' when you are done. I've heard of some installing a piece of pipe inside the cat, so it doesn't ack like an additional resonator.

Hey, so what if it's illegal? Me, I'd be more worried about polluting the world for out kids... :-)

Aerowill

Hollowing it is easy. Just break up the matrix with your favorite blunt screwdriver. The shell itself is very tough stainless steel--like the rest of the exhaust. Bear in mind that the original Audi part was super expensive ($500 comes to mind). In my experience, the 7A sounds bad with a hollow cat. Really bad--raspy and wheezy. I ended up putting a big race cat on mine and it sounded a lot better. Oh and it's illegal. Ha ha ha.

audithepeanut

Run it like the original Cat. gets rid of weird sounds and you get better performance,

I bought mine like that and then bought a new Cat for emissions

reddiamond

if your runing stock exhaust you cant tell the difference in sound