In a forced induction application, the intake manifold becomes pressurized. Therefore, the injectors need to overcome this positive pressure to provide the correct amount of fuel.

Say for example, you are seeing 5psi of boost and 43.5psi fuel pressure at the rail.The effective pressure of the fuel injectors now becomes 38.5psi and they are no longer flowing at 43.5psi. To overcome this problem, a boost referenced fuel pressure regulator can be used.

A boost referenced fuel pressure regulator (BRFPR) senses boost and raises the fuel pressure at a ratio of 1:1 with boost pressure. So in your example of 5psi boost and 43.5psi fuel pressure, the BRFPR raises the fuel pressure 1psi for every 1psi boost to make 48.5psi of fuel pressure at the fuel rail, allowing the injectors to flow 43.5psi (48.5psi fuel pressure @ 5psi boost pressure).

In a return type system, fuel is pumped into the fuel rail and an on-rail regulator restricts the amount of fuel that exits the rail and returns to the fuel tank, keeping the fuel pressure at the rail constant. A BRFPR actually controls the fuel pressure in the fuel rail by restricting more fuel as boost pressure rises, actually raising the rail pressure rather than keeping it constant.

A candle burning on both ends is twice as bright but lasts half as long.