How big of a port job can you do with a high-flow cat and still pass emissions? I don't really give a **** how it idles or how loud it is or anything, I just want to know if that one high flow will keep it legal.
Oh yeah, it's an NA. It's got a header and a presilencer now, but I'm thinking that I'll get a cat soon so I don't have to swap in the crappy stock one every year for emissions. I also like the deeper sound you get with a cat.

 

The ONLY porting you can do and still pass emissions is streetporting.
I'm not sure if that 1 high flow cat can do the job... I don't deal with emissions

 

I'm also gonna lean toward the Street port of a rally port (large street port), unless you have some serious engine management going on.

 

Oh yea, I also love the sound with a cat .

 

As long as you take the car out for a nice spirited drive before you get it tested to get the cat nice and hot, you should be fine with any resonable port. The cat would have to be one of Mazdatrix's "gray area" cats if you're gonna use the header and stock replacement cat back. Or you could have a custom one made. But the header will not bolt to a stock cat and the stock cat back.