Evolution MotorSports VTG Sport Stainless Steel Headers have been designed to increase HP and TQ on the 997TT cars fitted the OEM VTG turbochargers. Power is increased by ~18 HP/TQ. The medium length and 41.5 mm primary tube diameter design is perfectly matched for the exhaust travel from the heads to the VTG turbochargers for better boost response and power throughout the rev range. The smooth mandrel bends and pyramid merge collector offer superior flow characteristics as compared to the OEM headers. We have spent months designing our headers to optimize the efficiency of the VTG turbos.