I've spent a lot of days at a lot of tracks the last 5 years and I know most of the people racing BMWs in the US and a few in Europe. One of my close friends is a factory driver. KW is not a force in road racing. Their stuff is on a few cars in Europe. I've seen there stuff on a few European cars like the Viper that one at the ring, but on a comparative basis KW doesn't even show up on the radar.
I don't know of a US BMW team using KW. PTG uses Moton/Sachs and the factory team uses Sachs/Koni. Come to think of it, I can't think of any US GT Rolex team using KW.
I like GC for xover applications because you can choose spring rate and they use double adjustable Konis which are easy to adjust and have a long seal life. Koni have been used in track applications for decades. For the money and the support you get from Ground Control them they're tough to beat. Also, they supply bearings, bushings, rear control arms, and lots of other parts that are custom for the e46. Very few of the other companies just can't compete with that.
I'm laughing my a** off that so many people are in love with PSS9 or even KW for that matter. It is a total herd mentality. A bunch of people that don't know anything about suspension that have other people install their stuff because they don't know how to do it themselves telling each other that some average product is the best thing out there.
Go KW they're sweet dude.:thumbup: