Multiple codes, hunting idle, limp mode

[rtwaits]

Hi All,
I have looked at a 2013 X5 3.5 xDrive with 131,000 miles. I already own a 2012, plus other BMWs. This one starts perfectly, but then almost stalls, and then settles on a surging idle, from about 800-1600 rpm. The owner took it to the dealer, who found brass in the oil filter, which had torn pleats, suspecting work rod bearings or cam journals. I do not know to what extent, though the phrase "clogged with debris" was used. The car itself is very clean, and the dealer said otherwise the engine was proper. No major oil or air leaks. There were codes that may have been cleared; I used ISTA. The dealer was focused on the camshaft actuation, oil pressure and air plausibility codes. The dealer recommended engine replacement, but I do know many times dealers can be hyperbolic. I did not open the oil filter, but there was a fair amount of vacuum on the oil cap when I opened it while running. It did not stall when I did this. There was oil splashing about as I would hope it would. I did open the expansion tank cap, and the coolant was brownish (and filled to the top), but there did not appear to be oil in it (i dealt with that on an old E30). I did not see white smoke on start up or when revving.

The codes I have are:
2D55 VANOS intake not controllable
2C58 Charging pressure switched off as consequence
2EFE Combustion misfires multiple cylinders
2BEA Fuel air mixture too lean large deviation
2F01 Misfire Cyl 3
2F02 Misfire Cyl 4
2EE2 misfire several cyl; Damaging exhaust gas after starting up
2EEC Misfire Cyl 3;Damaging exhaust gas after starting up
2EF0 Misfire Cyl 4; Damaging exhaust gas after starting up
3429 Engine oil pressure sensor plausibility; pressure too high before engine start

No code for camshaft other than the VANOS related one - quite possibly a solenoid.

I did drive it around the block at about 25 mph, it seemed fine; did not stall or do anything bad, actually.

I have been doing a lot of searching, and i have seen an article describing an HPFP failure mode that disables Cyl 3,4. but I found that rather convenient. And does not explain the oil pressure code.

I want to go back and do a compression test on 3,4 and inspect the oil filter for myself. I've never replaced an engine before, and I know newer cars are fraught with peril about programming this and that (I did replace the head on the aforementioned E30). I do think that if I get it running properly, and get 40,000 miles out of it before the rod bearings completely give out, then it is worth getting.

Any insight is welcomed.