I finally got somewhere in my search for the vacuum leak, that must be causing my codes. First, I looked for loose or spongy rubber hoses coming off the SAP, and the F-connector attached to the intake elbow . They were fine, and felt & looked certainly less than 21 years old (fresher than some on my '09 HHR). Then I got out my cheap borescope to look behind and below the engine.

That's when I spotted a hose, unconnected next to the steering shaft (turned out to be a plastic tube), that was curved upwards towards an unknown spot. For the life of me, literally, I jacked up the left front of the X5, put a 3-ton jackstand under the steel subframe, and crawled under from the left side, Got this photo, but couldn't see where it is supposed to connect (the other end rises up towards a vacuum source above, I guess).
spotted it from above
it rises past the dipstick
from below, it is plastic

Can anyone identify where this open-end connects? I saw nothing while under there, and there sure isn't room to explore. My jack & jackstand are both resting on 1/2" plywood, and cutting thu it as I write this; I'll have to put the X5 back on the ground for safety.

And how does anyone actually reach behind the M54 anyway? do I have to take off the windshield washer tank? The only other way in that I see would be to remove the air dam? where the cabin filter housing is. Looks like the brake hose & other lines run through it.

__________________
01 BMW X5 E53,3.0i-5L40E, 7/13/01
topas-blau,Leder-grau,"resto-project car"

Here:
14 Lexus ES350,3.5L-U660E
09 HHR Panel,2.2L-4T45E
04 Chevy 2500HD,6.0L-4L80E
98 GMC Sierra 1500,5.7L-4L60E

Gone:
66 Chevelle Malibu 2dr ht.,327>441c.i.-TH350>PGlide/transbrake
08 Cobalt Coupe,2.2L-4T45E
69 & 75 C10s,350c.i.-TH350
86 S10,2.8L-700R4
73 Volvo 142,2.0L-MT4
72 & 73 VW SuperBeetles,1.6l-MT4
64 VW,1.2l-MT4
67 Dodge Monaco 500 2dr ht.,383c.i.-A727
56 Chevy 210 4dr,265c.i.-PGlide