Update. Looks like it was the brake-booster vacuum pump cover that was leaking. I pulled the cover, cleaned it up real good and put a little Permatex 98H High Tack Gasket Sealant on both sides of the o-ring that BMW doesn't sell....
I did see one company apparently does sell a gasket for it ~$18-$22 IIRC. Just took the X-for a spin and it's nice and dry....
