3
Yea it probably will but I went for it anyway. I don't know if the cat back will give any more power but milltek are bound to claim that it does but they look good and sound great, not too loud and the car isn't much louder at idle but you can hear the boxer sound and it's just right when you put your foot down. I've had my cat back on since the car was brand new and I'd say it's a must have as the cars have no sound at all without it. When I took mine for the remap they done a base run with just the cat back and it made 286bhp and 275ftlb on BP ultimate fuel. I then added the downpipe and cat a perrin induction kit and the remap and it went to 323bhp and 350ftlb. They said I probably would have had an extra 10bhp if I had done it with shell v power but I can't get it anywhere near me so it was pointless mapping the car for that fuel.