i mean hollow out the cat, i tried everything but it doesn't comes out . what's tool do you guys use

 

http://www.testpipe.com

just buy one of those and then you wont have your reallly expensive to replace catalytic converter messed up if you ever need to put it back

 

Yeah, get a TP for the track and a HF Cat for the street. It's only 80 bucks or so for a 2.5" carsound.

 

If you really want to clear out your cat just pull it off and smash a bar through the material. them bang on the outside for a while it will all break free and be gone. But then good luck passing emissions. Why not just spend the cash and get a high-flow cat?