According to page 83 of this:
http://clem.e46fanatics.com/BfestE90/BFestE90.pdf
The suspension is the same across all 3 series models, with the exception of aluminum vs. steel, although the car has a .02 inch height difference. Does this mean that they aftermarket tuners will find it easier to make suspension kits for the xi's? or possible to use i's suspension kits on the xi's?