Product page:
http://www.daddysscp.com/dcart4/prod...9&cat=8&page=1
The blurb states: "Manufactured from the same factory producing these headers for a famous JDM brand, where they are already proven to put down approx. 20+whp to the ground.". Back when I bought them the rumour was that these were tomei headers. After speaking with Mike @ gruppe-s, I am now convinced that these are GT-spec headers, possibly the same ones that Nick has.
The fitment on these was pretty bad. The stud holes in the turbo had to be drilled out to get the uppipe to bolt on. The header hit the subframe under the car. Rather than try to bend the subframe lip out of the way I have just removed it for now, something I am not really happy with. Overall a real pain in the arse.
When I bought these the main selling point was that they wouldn't lose the boxer engine sound that the stock headers have. I don't have the email from the vendor anymore but the quote was something like: "if anything, these enhance the boxer engine sound". Unfortunately, that turned out to be bs. They sound just like Nick's car (even more reason why I now think these are GT-spec headers).
The only positive thing, they did make some good improvements in midrange torque. I picked up about 11 Hp and 24 ft-lbs compared to a baseline run from earlier the same day.
Overall, if you don't care about the change in the exhaust note, and some fitment issues, these are great headers, which will give a strong boost to midrange torque. If you do care about the sound and the fitment issues, avoid these headers.