Ok I know that most turbo cars respond very well to removing the cat from the exhaust. I also know it is illegal in most states and wont pass a VISUAL inspection but my question is will it trip any engine codes.

Also has anyone done this and seem inprovments in performance.

I was also thinking about removing the factory muffler and installing a straight through/non chambered muffler instead.

 

Yes it will throw the CEL.

You only gain 2-4hp when removing the cat. What you could do is have a test pipe made, and use that when you go racing or something. A high flow (race) cat will be just fine. Get a magnaflow muffler for they are straight through.

You will see more gains through a 3in downpipe. then a 2.5 cat-back or go 3in all the way.