http://www.realoem.com/bmw/showparts...13&hg=25&fg=05 From that link, parts 2, 4, 5, 7, and 14 wear out causing the sloppy feel.
UUC (and others) offer a delrin version of part number 2, I highly recommend this.
5 is the shift lever itself which has a plastic ball that wears out, just get a z3 shifter to replace this, I chose the Z3 1.9L lever.
14 is a small sponge that wears out and causes trouble selecting gear, it is easiest to just buy 12 and replace the whole thing.
It would be really nice if someone made a stiffer version of 4 but I have never seen one.
Part 3 is the bitch clip, search on that before you try to take it off.