The fuel pressure should hold for at least twenty minutes.
However, the fact that pulling the injector lead doesn't change anything makes me believe that the wires running to that connecter have broken. Remove it again and probe the leads with an ohmmeter. You should get a reading of 5.4 ohms. If this checks OK, then that injector may have failed. The best way to check this is to remove the fuel rail complete with injectors and place a piece of cardboard so as to catch any fuel. Disconnect the hot leads from the coil and crank the motor with the starter. The injectors should spray a fine mist on the cardboard. Have a fire extinguisher nearby-just in case.