The Tubi Style street exhaust system for the 997 Turbo is a mojor improvement over the factory part both in terms of sound and performance. Because of the free-flowing design, the system is responsible for 15-20 horsepower gains, and also produces a much more pleasing exhaust note. During normal diriving and highway cruising the sound is very similar to stock, without any increase in cabin resonance. During hard acceleration the free flowing characteristics take over and create a much sportier sound.