In your first post you asked about going to coil overs which would be for all four corners. If that is the case there are many threads you can search for information about the change. I don't recall anyone saying they were sorry other than a few that bought inferior products. I recall there is a supplier that many have used and have been happy with but I don't remember the brand.

Coil overs are completely different than the stock X5 suspension.

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas