If I were to drill a hole in my cat for more flow, just a 5/8” hole, not gut the cat, would I get boost creep?
Trying to get a bit more flow, but not be too loud with a midpipe.
On a PFC and stock intake and apexi catback.

 

why dont you just get a midpipe with high flow cat and not compromise the cat?

 

I seriously doubt a 5/8" hole would make any sort of difference. Also the substrate in the cat is hard and brittle, if you try and drill it will most likely all crumble.

One of the main restrictions on the stock main cat is the flange for the inlet and outlet. Having flanges with larger ID's welded on can make a difference.

Boost creep is impossible to predict, each car reacts a bit differently. If you want more flow you're going to have to accept what comes with it.

Dale

 

Don't screw with a well working stock cat in CA if you need it for smog. The car has a hard enough time passing the sniffer.
Go buy a high flow cat from rx7.com

Get their downpipe too if your car is still equipped with the stock downpipe and pre cat.

 

I have the JDM downpipe without the precat already. I also have a spare cat just for CA smog. But I’m gunna go ahead and listen to Dale and the first commenter and get a highflow from rx7shop