I'll probably sound like a broken record here but unless you're an expert on these differentials, they are best left to a pro like Dan at Diffsonline or Metric Mechanic. There are so many little things to setting these up. If you screw up one of them you're going to toast some expensive parts.
'03 330i ZHP - Stock-ish
'02 330Ci - Megasquirted, E85'd and tuned by PFTuning.com