I installed the Gruppe-S header, overpipe, and heat shield this weekend. I hadn't seen anyone else on here with the Apexi RS Evolution Extreme catback on here, so I figured I would post up a mini review.
First off, the Gruppe-S stuff is great for the money. The fitment was spot on and there was extra hardware and tape in the box in the event you screwed something up. The only minor grip I have is you have to use a swivel to tighten the nut on the driver's side manifold flange. I prefer not to do that when using a torque wrench. The hardest part of the install is removing the heat shields from the stock overpipe.
The exhaust tone is perfect at idle. It is quiet and lobes. The UEL and boxer engine sound fantastic there and with light throttle input. At 3000-4000 RPM with moderate throttle input, however, the rasp comes on. The rasp was there with this catback before I added the header and overpipe. Above 4000 RPM sounds great with enough anger to keep me happy. I think I'll look into adding a resonator to the catback as it doesn't have one. I've had great results with Vibrant resonators in the past.
Youtube:
[ame="https://www.youtube.com/watch?v=WOENIeGoD3s"]BRZ Gruppe-S UEL header and op with Apexi catback - YouTube[/ame]
Google album with fitment photos:
https://goo.gl/photos/dx27j2S6fvqThkYd7