I installed my new TurboXS Catback Exhaust System last night, it took only like 2 hours to install which surprised me... Anyways, where the stock meets the aftermarket right after the cat. conv. there is a doughnut gasket. The hardware kit that came with the exhaust comes with 3 gaskets and they don't fit around the doughnut gasket. Is the doughnut enough to seal it, or was I supposed to put on the copper gasket also?