One thing is certain... if you have the N54, you will be forever at the mercy of a potentially faulty HPFP. Yes, I realize BMW has extended warranty on them.
The F30 N55, and N55 built after March 2012 have a different/redesigned HPFP than what was available via older N55 and all N54 motors.
2016 M3 - current
2013 ActiveHybrid 3 - sold
2012 M3 coupe - sold