I bought a carbon trunk and diffuser off a couple of fellow enthusiasts. A friend of mine who is a BMW tech did the install while I sat around and watched, making myself useful every once in a while. I would have had no problem doing the job myself, based on what I saw, but he definitely did a more precise job in a shorter period of time than I could have done, since he has more experience with the sheet metal and body of the car.
The trunk is Seibon. Fit is 7/10 with some weird gaps between it and the sheet metal. Install wasn't too bad according to him. The weave is wonky in some spots, but for the price I got it (less than half of retail for a brand new trunk), I can't complain. It's OEM style, so no fancy lip. The butt looks a little naked now (well.. except for the awesome carbon fiber), so I'm probably going to get an ABS spoiler painted BSM from JBSPEED here on the forums. Other than that, the trunk needed some of the holes for the license plate lights and the handle shaved just a little, but no big deal. The weirdest part was that there is a hole for the keyhole enclosure, but there is a piece of fiberglass behind there that is part of the structure of the trunk lid blocking you from actually inserting the key enclosure there. Not a big deal for most people since the newer cars don't have this key hole, but for my it's a little weird. I knocked 1/10 off for the fit for that reason, even though it's not a big deal for me either. I never use that keyhole.
The diffuser is Scopione, the first generation one, bought new from someone who had sold their 1er a long time ago, had never mounted it, and has been storing it since. Fit is 9/10 if you don't take the tabs into account. The tabs needed to be shaved down quite a bit with a dremmel, and even then it wouldn't fit perfectly. We ended up taking the rear bumper and fenders off altogether, then attaching the diffuser with the tabs and two screws to the bumper, and finally re-attaching the bumper and securing the diffuser with the rest of the screws to the undercarriage. Once the hassle of attaching the diffuser was done, it looked great and sat mostly flush against the bumper. Weave on this piece was very good, probably a little bit better overall than the Seibon trunk. Though it had a few bad "splotches" in a couple of more hidden areas that are much worse than any part of the Seibon weave.
Overall the weave on both would be about a 7/10 - a little bit crooked in spots with some splotches that are just bad, mostly in hidden areas that are a little more intricately curved. Weave is tight all around for both.. no resin showing through, just crooked spots. The finish itself is good, though, with a good color to the carbon fiber itself, and plenty of smooth gloss (hopefully both have UV blocking finishes)... Overall I am happy considering I got these both for the price of an iPad. Way better Christmas gift than that
Overall, I am very happy. Here's a couple of quick pictures I took:
Thanks for looking. Real photoshoot to come when the weather doesn't suck.