And the original (now outdated) SIB 110803 from December 2003 ... shows the problem has been around a while though. Although I still don't understand why some of the part numbers don't come up on realoem ? (e.g. E53 dipstick guide tube and E53 oil separator repair kit) Weird. Also adding the December 2006 update of SIB 110803.

SIB 110803 updated again. Now dated March 2009. (Last updated February 2009). No real changes to it, they are just identifying specifically that the affected cars all have the M54 engine.

A dealer here in MN advised to drill a hole below the o-ring. What the hell for. I did it, but I have no idea... The old dipstick guide has a hole as well. Has anybody drilled a hole in their guide?

Say what? So you're just drilling random holes in your engine? You realize that your engine is designed to operate with a certain crankcase pressure (10.0 mBar for the M54 & M62, and 22.0 mBar for the N62/TU) and that by drilling holes, I presume, you are now reducing that pressure. (Reminds me of the Three Stooges episodes where they get a leak in their boat and drill another hole to let the water out). Anyway, can you snap a couple of pictures of where these holes are and tell us how you made them? Most importantly did it help?

Is the hole out in the open??? That would be a vacuum leak if it is! So now if you get the lean mixture faults at least you know what it's from.