I did a quick search but didn't pull up anything specifc.

I was just able to get a cat (carsound 94006) which has 2.5" ID for $60 new and I was planning to use it with my car but I've found that my header has a 57mm ID (~2.25") and my exhaust at the flange is 52mm ID (~2.04"). Now I was wondering how badly this would affect the flow if I did use the 2.5" carsound. If it's detremental I guess I'll have to return this one and buy another one for $100.