Problem is that emissions usually means restricting performance.
That would be a better question?
If we were willing to take a hit in performance, I'm sure having a cat wouldn't be a problem...
Most cats, even "high flow" ones, are restrictive.
It's still going to hurt performance versus a "straight through" exhaust system.
How do you get around that?
Run a BIG )@*$%( cat...or multiple cats.
Problem is that these things cost money.
I'm trying to get a pair 'o Metalit 3" cats from Japan and run them in parallel.
One of the big rotary shops in Japan (FEED or Panspeed) did this on a "700hp" 13B turbo with good results.
Figure this would be fine for my needs which is only 500hp.
Metalit cats are very hard to get in the USA, and they are very expensive used even in Japan.
-Ted