I assume this isn't a normal thing, but it's definitely odd. The exhaust on the drivers side has a nice lopey-cam sound to it, but the passenger side is much faster and more even sounding, almost as if that bank of cylinders is firing more quickly. When I turn on the AC, both sides sound the same -- like the passenger side. There is no check engine light, and I just changed the plugs; they were all clearly working due to the slightly blacked tips. I changed plug wires a year ago when I bought the car, and it has done the same thing before and after the change. I do know there is an exhaust leak on the passenger side at the manifold collector. Car has Billy Boat headers, high flow cats, and a Corsa catback. Any ideas? Surely a minor exhaust leak wouldn't cause the two banks to sound different?