So, there's a new test requirement coming up here in the UK - that a car that was factory fitted with a cat needs one fitted for the annual MOT testing, regardless of age.
I had my IROC de-catted about 18 months ago, and now it looks like I'll have to stick one back on.

As I have to get one, does anyone have any suggestions for one that's pretty free flowing?
Hopefully, I'd like to stick a 3" exhaust on at the same time.

Thanks all

 

Magnaflow has a fantastic reputation for a high flow,quality cat. I run one and have never had a problem passing CA smog.

 

Does it just have to be there or does it have to work?

If it just has to be there you can a ways just put an empty shell in there or cut an old cat in half and fit it around the existing pipe...

 

It's a bit of both to be honest - if the cat's not present it's a fail, but they do use a probe in the exhaust to check the emissions too.