ok i have a apexi gt spec catback exhaust for my car, what catalytic converters will mate up to a apexi gt spec. and what downpipes will work with my application, i looked up the specs of the catback and it says for pipping diameter is 65mm-75mm-85mm and 115mm tip, now im not sure if there is just different diameters in the exhaust or if it had three different options for the exhaust when you order it.

 

you will need a 65mm I.D. catalytic converter = 2.5 inches. Doesn't have to be exact, but around there.

 

ok thanks