I can tell you this, i have had 3 Xi's. In the north east, the springs break all the time. BMW paints a little colored stripe on the spring to differentiate. You really need your VIN to determine what the original spring on your car was. Mine i think are silver or white stripes. Replacing them is very easy, just make sure you have a long prybar or crow bar. i use a 4 ft harbor freight claw wrecking bar.
BMW and Pelican will tell you that the springs used on each car depended on the individual package or various options for each car. Some people say that all springs for the xi's are the same. If they are all white/silver then i believe it.