No diesel experience, but this is what I'd check.
How are you reading codes? Generic OBDII code reader? Does it have live data that allows you to see the fuel pressure? A BMW code reader like Carly will let you see the fuel pressure on gas engines. Gas engines with HPFP's (N54/55 gas turbo engines) have a low pressure fuel sensor which is readable with BMW capable analyzers.
Checking pressure at rail, even if possible, will require special tools as pressure could be >2000 psi. There may be a port downstream of LPFP that you can check to confirm LP pump runs. Should be ~75 psi for gas engine anyway. Can you crack open a low pressure fuel line while cranking to see if nay fuel is being pumped?
Check connection at LPFP in tank, accessible under back seat. Gas E70's had problems with this connector corroding, overheating followed by no fuel pressure. How did Bimmer Performance Center code your car? Did you deliver it to them or did they do this with your laptop connected to the X5? If the latter, perhaps they can scan your car for codes.