First off, the most obvious thing is to check if your lower control arms are bent; it's not uncommon. As for bushings, you're dealing with upper and lower control arm bushings, and there's both inner and outer (parts #'s 2,3,6 & 8 In diagram below), and then there's the trailing arm bushing (part #4). Shouldn't kill your wallet too much; about $15-$40 each, depending on which ones you might need. Inspect them, visually compare one side of the car to the other, and wiggle them around to see how much play there is. You'll find them just about anywhere, definitely Pelican & AutoHaus, Bimmerworld and Bimmerparts should have them too.