When I switchover to an aftermarket exhaust, I will be getting a tuner to turn off MDS. Its my understanding it makes performance exhausts sound ridiculous. My stupid question is this, Disabling the MDS ill affect my gas mileage how much? I need my muscle car sound, because my 64 Cutlass is being sold, I'm out of room for my man toys. PS Anyone interested in a 64 Cutlass convertible??