The TurboXS 08-14 WRX & STi uppipe is manufactured to exacting standards. The smoother flowing TurboXS uppipe will increase exhaust flow to the turbocharger, increase HP & reduce turbo lag. The TurboXS uppipe provides a flex section to help with fitment and is constructed of stainless steel to improve durability. The TurboXS uppipe has an inner diameter of 45mm; this is the exact same size as a stock Subaru turbocharger inlet. This promotes the best possible performance throughout the entire RPM range by maintaining exhaust velocity. Oversizing the inner diameter of the uppipe slows exhaust velocity and creates turbulence as it enters the smaller inlet of the turbocharger, potentially even hurting turbocharger spool up. Though the 08-14 WRX & STi does not have a cat in the factory uppipe, this product will still improve throttle response and drivability. This product does not include an EGT bung.