Why do I need this?

Your car doesn't actually keep your exhaust valves open and only partially open in some cases and models. Although your car does have a "loud mode" (sport / race / track) that opens the valves, in reality it does not actually keep the valves open and even closes them at certain RPMs, throttle positions, gears and speeds. The 11MODE Exhaust Controller gives you full control to open your exhaust up to 11.