I've not done them on a BMW, but coil springs should be coil springs, unless they are coil overs.
Whenever you cut a coil off of a spring, you not only make it shorter, but you raise the spring rate. Just do not do too much at once. I know on our Mustang one coil was just about perfect in the front and back, but you may wish to start with just taking off half a coil to see how much that gets you.
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