I'm baffled by this entire thread.
This is basic physics.
Things move from areas of high pressure to areas of low pressure.
The rail must be pressurized to a point higher than the manifold or nothing will move when the injector opens.
For flow to to be predictable, the delta between the rail and the manifold must be the same at all times. That's why we have a pressure referenced regulator on the fuel rail. So that every time that injector opens, there's 43.5psi of pressure forcing fuel into the manifold.
There has to be a fantastic amount of bullshit out there for somebody to even consider what the OP is asking about.