Ideally, and what the 1:1 FPR does, is keep your fuel pressure at that 43.5 psi, regardless of boost. Lets say you boost 10 psi, adn then the FPR will raise fuel pressure to 53.5 psi, so fuel pressure remains constant, while the acutal injector pulse width will add fuel instead of more fuel pressure. Even though the fuel pressure is 53.5 psi, the differential pressure between the intake side and fuel rail side of the injector, is still 43.5 psi.