Other than putting hi-flow cats to get rid of the exhaust smell, what have you done to eliminate getting exhaust fumes in the cabin? I've read about blocking the side vents in the trunk, but that's not a good idea. Do the rubber flaps in the vents go bad and has anyone replaced it? Has anyone tried a rear diffuser and did that help? And the guys who converted to side exit exhaust, did it make the smell worse or better?