I finally had the time to Spring clean the car and take care of this issue.
Overally the XPEL suggestion to use the Westley's Bleche-Wite worked very well, although it was a bit nerve racking putting that caustic stuff on.
After a thorough post-Westley's wash I clayed the entire care, put on the XPEL bra 'sealant' and then waxed.
I'm pretty happy w/ the results. Note that the day was heavily overcast, that's why the pics kinda suck.
2008 E90 M3 (IB, Premium, Tech, Cold Weather packages, PDC, 6MT, 19")