Let me start by saying that I just got my Boxster S in February and just recently found this site. In just a few weeks I found so much invaluable and helpful information here at renntech, and also at babblers, so I'm trying to give a little back. It's not much, but those in the market for headers should probably take the time to read this since it's hard to find out REAL information on these products. I also want to be very clear that I have nothing to do with the manufacturer or seller and have no vested interest. These are just my thoughts, and although I do not have any Porsche experience, I do have a lot of tuning experience so I'm pretty familiar with what is and is not a quality product.
After putting the car in the air and looking at the bottom of the engine I immediately found the need to change from the stock headers. I do not at all like their design as they appear very very restrictive. I don't have a ton of money and somebody on Babblers.org had suggested the Turbowerx headers so I gave them a shot.
Install
I will say very plainly that headers are MUCH easier to install than a muffler is on this car. I was actually quite surprised how easy it was to take off the old header and put the new one on. I used PB blaster on all the bolts and let them sit for ~1 hour before removing the old bolts and not a single one gave me a hard time. I did not expect that at alllllll. :)
To note, the Turbowerx headers have 2 bolts that are very tricky to tighten with a ratchet and likely will need a box wrench to tighten down all the way. The plastic shield on the passenger side of the car I loosened up to help get to them. That was a simple removal of 2 screws and 2 nuts.
Quality
All I have to way is "wow." I have seen a number of headers in my day and none are the quality of these! I spoke with the company and the guy said he does them himself, although he outsources the flanges, he does all the welds and developed the tubes himself. Impressive and made in America! Woohoo!
The steel is beautiful, the welds are perfect and clean, and the flanges are very thick (1/2"!!). The F1 merge collectors are the perfect choice here also in my opinion. Bravo all around.
Performance and Sound
First a quick note on sound. The cats are deleted (Yay CEL!) and the pipes are thicker. This by itself definitely made the car sound throatier and a little more imposing. After also putting on an aftermarket muffler it's very loud, but regardless of muffler this WILL make it louder by a noticeable amount, although not too much.
As for performance, I do not have access to a dyno so I cannot give a perfect answer here. The website shows a dyno graph that illustrates a 22hp/18tq increase for the 3.2L and even more for the 2.7L. The seat of my pants says: "I believe it." The car really starts pulling anywhere over 3k rpm much more than before, and once it hits 5k...it's a crazy difference. Wow. The only other modification I had was a K&N filter, desnorkled, and now also a performance muffler (but the muffler didn't make a difference really).
Other than when I put a turbo on my NA car years ago, this is simply the best single-mod performance difference I have yet encountered-it's THAT good. Enough said.
Final Thoughts
I have absolutely nothing bad to say about these headers. They're CHEAP, or relatively though. They cost me $799 and I bought them during a free shipping promotion. Sweet! For that price I in no way expected such a beautiful piece or such a dramatic increase in performance. Best bang for your buck I've seen in my time. I know the pics aren't great but they were taken with my Blackberry so my apologies, I tried! Please feel free to ask me any questions if I left anything else out.