I'm not positive here, but I *think* he's talking about gutting a CATALYTIC CONVERTER! You guys are some sick bastards, lol.
Anyways, the easiest way to do it, is just to take the outside cover off of the cat, and replace it with a straight pipe, then put that cover around the pipe so it looks like you still have a legal cat there. Or the other way is to get a big ass drill bit, and just drill away until the inside is all gone.