Low fuel pressure

Dear Sir,

I have a generic question to ask, doesn't relate to a car but to a motorbike, but I belive that the basic technic is the same.
My fuel system does not manage to get the right pressure while priming, neither while idling or running on 6000 rpm. The pressure, according to suzuki should be 42 psi but it constantly stay at 37 psi.
Fuel pump works correctly, so watching your video about fuel pressure regulator I tried to disconnect the vacuum line while idling and suddenly the fuel pressure shots up to 42 psi.(Right pressure)
Is the regulator to be faulty or is too much vacuum going on in there?Can I use the bike with vacuum line still disconnected?
Thanks for the help you would give me

Alessandro Roscioli