What kind of Tires are you running?
I recently replaced Michelin Pilot Sport PS2's with Toyo Proxes 4 and notice unpleasant body flexing during fast cornering. For instance if you're just driving straight on a highway and turn the steering wheel back and forth you can easily get the body to flex.
The suspesion parts are all OK so I was looking at the Tires. The PS2's didn't so this. The turning was crisp and precise. I was guessing these Toyos being an "all season" tire were harder than the Michelins so they transfer the forces up to the bopdy where the Michelins gave more and the forces went out the tires which may be why they wear out so fast. Well less than 20,000 miles and I was seeing thread.
1995 540i Manual build 1/95