Fuel pressure after ignition key off, etc.

I have been checking thru some postings but no solid info yet. So thought would try starting a thread.On key off, my fuel pressure drops to 0 almost instantly. Some mechanic told me this might be the check ball on my in tank fuel pump. Could this cause any driveability issues?
Another possiblity maybe, fuel pressure rail has a aeromotive billet aluminum fuel pressure regulator. Could the regulator be causing the quick drop? Also am wondering if this is the correct regulator for a normally aspirated engine setup. On detaching the vac hose ,fuel pressure goes up to around 47 psi , vs 42 with engine running and vac hose connected.Still trying to eliminate issues on my car
TIA,
Hink

ok, still sorting things out here, adjusted the FPR for ~40 with vac hose off. Disconnected my battery for a while will see what happens, with my issues
on the car.
Thanks,
Hink