It looks like a slow build but I suspect the rental tester + adapter + swapped schrader valve probably didn't allow max volume flow to the gauge 100%. But at full throttle the fuel pressure stayed pretty solid.

I have not had hard starts at random. This X5 may run like crap most of the time, but it is eager to do so and the engine starts promptly every time.

__________________
2003 E53 X5 3.0i 5MT
2003 E53 X5 4.4i