I just got my new jdm dc sports stainess header, 2.5" carsound cat, and rsr catback. Do I need a new gasket between the header and the cat? I know inlinefour.com offers one to go with the header, but i think it's a merger to fit into a 2" cat. I think I'm looking for a donut gasket... possibly from an sk2? I'm looking to buy everything before i put it on so I don't run into any problems.