Using my generic scan tool we keep in the X5, it came back with P1093. Perhaps this is the issue... I grabbed my C310 BMW tool from my car and used that for the live data and codes. It showed more codes...

EC Trimming, oxygen sensor before cat converter bank 2
E4 Fuel trim bank 2, permissible range exceeded
E3 Fuel trim bank 1, permissible range exceeded
F2 misfire cylinder 5
F0 misfire cylinder 3
EE misfire cylinder 1

The coil packs are original, except for one we replaced over the summer due to a single cyl midfire code. I wonder if the other 5 need replacement. 185k and 2005 on the originals! Spark plugs only have a few thousand miles on them.

Started the car this morning, ice cold engine (below freezing ambient temps here this morning) and at idle the air mass flow is 21 kg/h. I revved it a bit to 2,000 RPM and it went up around 60ish kg/h. Should verify the readings at different RPM later, it was early, had to check before my wife took the car to work.