[Dmitry at Pelican Parts]

From what I've read and heard, the N54 motors are prone to hpfp failures, so you may be right to assume that. I'm including a link to one of our site's DIY tech articles on the fuel pump test and also to an earlier thread where this is discussed - hope this helps you out a bit in troubleshooting.

https://www.pelicanparts.com/BMW/techarticles/BMW-3-Series-E90/FUEL-Fuel_Pump_Testing/FUEL-Fuel_Pump_Testing.htm

https://www.e90post.com/forums/showthread.php?t=1331368