Engine swapped Jetta won't start unless ignition is left on for 5 minutes first!

[Rynny]

Update to my no-start/long-crank situation:

I may have found a problem to look into, so I just opened my passenger door and disconnected the fuel pump (so I could read the rail pressure without it priming), and turns out my rail was at 1.02 bar and low side at 1.06 bar after sitting overnight. I would also like to note that my 103-2 (Fuel Pump Adaptation Value) is -4000, while the VCDS site says spec should be +/- 1000, is this an issue?

Priming it sent them up to 5.06 and 5.28 (high and low sides respectively)

Then disconnecting the fuel pump again, the high side slowly leaked down to 4.2 bar over the period of 2 minutes while the low side stayed at 5.2

I am now suspecting that I have a bad fuel pressure regulator and/or leaking injectors, I will be testing for wet cylinders tomorrow. I really want to fix this issue because waiting over 5 minutes just to hope it catches sucks, I want this build to be ready for cruises haha