I think mine is plugged, so would taking some kind of rod and pounding the hell out of it to "hollow" it out be a good idea? Or should I just have some muffler shop make me a straight pipe?

 

The stuff inside of cats is very toxic, I've seen people take a long pipe to hollow out there cats without any protection and I cleared the area quick. If your state has emissions then you'd just be screwing yourself over. Short answer: yes, but I'd rather put in a pipe, save a few extra pounds if anything right?

 

dang....me and my friends had at it the other day...like face to face with honeycomb cat crap....im still standing today..and i had NO protection and i did it in my friends room....a shop wanted to charge me 80bucks to hollow it out....or 45 bucks for the strait pipes...

so i mean if u wanna save cash your gunna be fine hollowing out the cat...now the precat..im just replaceing with a downpipe.....

 

Don't worry about it. Wear a face-mask and use a long crow-bar... Just prop it up and start pounding the crow-bar into the honey-comb crap. Eventually it'll start breaking up and you can turn it upside down and shake the big chunks out. It takes a little while to get all the stuff out, but it's actually kind of fun and satisfying. Especially since it'll make your car faster... hehe.

Just do it yourself, especially if you don't really have the money to buy a nice DP/Presilencer. I'd guess that a stock hollowed cat will sound a lot better (quieter) than some aluminized custom piping (won't flow as well, but whatever, it's free).

My s4 N/A had a K&N drop-in filter, wired open 5th and 6th ports, gutted cat and a stock TII cat-back. It was actually faster than my TII when it was stock (although the TII was pretty tired, lol)...