HKS Sport Catback Exhaust for 03-06 EVO 8/9 is designed to reduce backpressure and increase exhaust flow for greater peak power and a broader torque band. Each Legamax and Sport Exhaust application utilizes a specific muffler design and shape along with the appropriate piping diameter to maintain low-end torque while maximizing high-end horsepower. All Sport systems are made from polished SUS304 stainless steel piping.