My roommate has one of those apexi tunable mufflers and it still drones inside the car even with it restricted down. (b16a with high flow cat, header, 2.5 inch custom cat back) So i really dont see the point. If someone came up with something that had a lot of adjustability in sound and really worked well it would be great and probably sell. But even still there isnt too much of point in my opinion, considering that changing other parts of the exhaust system make a huge difference in sound as well.