I have a stainless system under my CSI. it has been especially designed for the CS(i). Besides retaining the CS sound, it also added a few bhps due to some adjustments in the final muffler. I have to admit I was sceptical about it, but now I have it, I like it. This system was also build in the UK. You can see this system in the following link: http://www.uitlaten.com/main.html then choose "uitlaten" from the top menu, then "BMW" from the left menu, then "3.0csi"