I am in the market for a high flow cat, for my '98 GSR I understand carsound makes one of the better ones and I was just wondering what inlet/outlet diameter I would need with a Comptech 4-2-1 header and Comptech Catback exhaust. Do I need to have my O2 sensor welded to this cat? Also, my current oem cat has only about 45,000 miles on it, is it worth replacing with a high flow, and am I going to notice any remarkable increase in hp or torque,(I also have an aem cai) and does a high flow cat also increase the sound db's with my current setup.
Thanks for your input.