From what I know from Milltek Sport in the UK, the catback provides a greater power increase than the headers/cats. The headers/cats facilitate a sharper throttle response with quicker time to RPM. The catback gives you power, looks AND the right sound. I'm sure someone will dyno the catback only. I can't do it here, the Cayman is gone for a 997TT we are in the middle of tuning. -Pete