crwarren11,
Very nice write up. Great details and $950 labor saved.
I went through similar with my booster
http://www.xoutpost.com/showthread.php?t=96360
Fully agree with your assessment that inside the booster should be perfectly clear and clean. My X5 with oil ruined booster only had a hint of oil residue in it but was fully trashed at 98k miles. While my E39 booster inside was brand new looking clean at 185k and still working great (looked in it when I changed mater in e39) now at 210k miles.
Clearly BMW has massive vacuum issues and broken 1 way valves on a lot of the 4.4/4.8 motors. Did you notice the replacement vacuum line now has a second 1 way valve in it.
I called BMW North America and registered the issue along with a formal complaint at dealer. Neither seemed to care much but facts on the safety recall still stand. I suppose we might never know why they did not include all 4.4/4.8 motors.