Your friend’s fuel issue seems a lot like the intermittent no-start, low fuel pressure issue I have been debugging (3-series) for over a year now. It has defeated three dealerships and two independent mechanics so far, so I’m taking over the diagnosis now. No clue yet but today’s cars have too damn many computers in them.
which engine is that? I had an N54 335 for 5 years too, even E36 era BMWs have vastly superior error logging compared to JDM from that vintage. I hope you find your issue, but if it defeated dealerships it sounds troublesome. Log some live data with INPA if it's an older one, I have no experience with BMWs post EXX series to drop any advice...
Yea, N54. INPA helps confirm things, but just the idea that you have to pour over logs to diagnose a system that should be simple and straightforward... sigh. My last car was from the '80s and you could wrench pretty much anything you needed to without having to negotiate with a dozen computers running the show.
