After my ho conversion, I replaced the stock fuel pump with a cam 255lph pump. The pressure in the rail would hold after the key was turned off with the old pump but not the new one. Is this a problem? Fuel pressure is 35psi with vac and 42psi without when the engine is running. Maybe there was some check valve in the old pump and not the new one. Is this correct or is it possible an injector suddenly stuck open?