Thread: Cat?

Ok I was going to have a catless 2.5in downpipe for my turbo setup, but the question is, would I have to tune the computer for it or can I just leave it? Im going turbo so I am not getting headers. And I have a 2.5in turbo downpipe already so I am going 2.5in. But I am also asking out of the random blue, what is so much better with a 3in over 2.5in.? Thanks for the help.

You will have to tune out the rear o2 code with no cat.
3" flows better.

2.5 will limit you.

3in is way better.

Ok from what I am understanding, I should change my turbo downpipe to 3in and have a 3in catless downpipe. Is there a way to make it so if I get tested for emissions that it reads out legal?

You can have it tuned out as a do not report. So you will still have a downstream O2, but does nothing. You have to have a downstream otherwise you will still get a CEL for one not being present.

Originally Posted by Classy Pontiac

Ok from what I am understanding, I should change my turbo downpipe to 3in and have a 3in catless downpipe. Is there a way to make it so if I get tested for emissions that it reads out legal?

Not if they do a sniffer.