Fuel Pressure Check (Lack Of Power)
WARNING: This page does not describe the selected car, but rather 37 other vehicles, including the 2005 BMW 760i, 2004 BMW 760Li, 2003 BMW Z8, 2003 BMW Z4, and 2003 BMW X5. However, it is still accessible from the selected car via links, so may be relevant.
Run engine at idle and check fuel pressure. See FUEL PRESSURE REGULATOR . Disconnect vacuum hose from fuel pressure regulator, simulating wide open throttle. If fuel pressure does not increase 5.8-10.1 psi (.40-.71 kg/cm2 ), replace vacuum hose and repeat test. If fuel pressure still does not increase, replace fuel pressure regulator.