On the MFI system, since the fuel injectors injector the fuel into the intake manifold, the system needs to operate at a high pressure to inject the fuel at a good velocity and to help atomize the fuel charge as it enters the manifold. The fuel system pressure is extremely important for the function of the fuel injectors. The electric fuel pump provides more than enough pressure and the fuel pressure regulator has the job of bringing that fuel pressure down to a level that the injectors need and help to stabilize any surges the fuel pump might create.