I have no experience at all with aftermarket fuel injection systems, (and I have no desire whatsoever to learn about them) but all the OEM systems I've worked with had a boost pump in or near the fuel tank, and a pressure regulator between the fuel rail and a return line to the tank. Some of them were vacuum modulated so a drop in manifold vacuum resulted in an increase in fuel pressure. That's been the basic design of factory FI systems since the mid-1970s.

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!