If you set this to 65 psi AND referenced it for boost, would the pressure go higher than 65 psi?

http://www.jegs.com/i/Aeromotive/027/13301/10001/-1

 

You will get 1 PSI of pressure extra per PSI of boost you have. As a word of advice, you will drop pressure equal to the vacuum the engine pulls as well if referenced against the intake. If you reference against the charge piping you should have a constant base FP until boost comes on. I would probably reference against the manifold, it makes your injectors look smaller which can help idle tuning especially with bigger injectors. It's also the way that the vast majority of OEM EFI setups are set up. A notable exception being TBIs actually.