HKS Hi-Power Exhaust - Subaru WRX / STi 2002-2007On this page, you are looking at the HKS Hi Power Exhaust System. This exhaust system improves the performance by lifting the restrictions found in the OEM exhaust design. Details: Larger 3" piping diameter and smooth bends limit turbulence and restriction under acceleration 304 stainless steel materials Minimal bends in the design Increase in both horsepower and torque Improved throttle response Reduced turbo lag Deep tone under idle with an