[e90pilot]

I've got an issue that's currently driving me nuts. I've got a 2A82 (stuck intake vanos solenoid) code and I've tried almost everything. I've stumped my mechanic, other BMW techs, and 2 BMW dealer shop foremen.

Background:
I just resurfaced/rebuilt the head. This was and still is a nightmare. The first shop couldn't source valve guides, but was able to clean and resurface the head. After about a month of getting nowhere, I took the head to a different shop that could get them. It took 3 weeks to make the guides and install them.

My mechanic tried to assemble the head but noticed we had 1 missing valve and 6 missing eccentric shaft bearings. It took too long for the shop to look for the missing parts so i just ordered new ones, but the first shop did eventually find the missing valve and bearings. After re-installing the head the car wouldn't start because of a bad CAS module. Apparently it's not supposed to be disconnected for that long. Another 2 weeks go by getting a replacement. The car started and ran without issue until the next morning where the vanos code showed up.

What's happening:

The code only appears at idle with SES light. If I clear it and drive it around the code does not return until the engine idles for a bit. They only other noticeable symptom is the engine revving to ~1700 rpm then returning to idle as if I rested my foot on the gas pedal for a moment. It does this once just after start-up. Power seems fine, but I haven't driven it for 2 months so I'm not sure.

What I've done:

Swapped/cleaned/replaced both Vanos Solenoids
checked and timed camshaft multiple times
check hook rings and seals
replaced oil cap
replaced wires to cam sensor and solenoid
checked cam and crank sensor
used thicker oil
checked oil pressure
pressure tested the head

Nothing worked or revealed anything

What the culprit could be

My mechanic is convinced that low oil pressure is causing the fault but we can't find where it's being lost. The current theory is pointing back to the first shop. If they managed to misplace a valve and 6 bearings, what else is missing? Maybe and oil plug? The last thing there is to try is replacing the cylinder head with a new/used one that know to be good. We're out of ideas here.