Recommended Procedure
WARNING: This page is about a different car, the 2008 Ford Pickup, 2008 Ford F550 Super Duty, 2008 Ford F450 Super Duty, and 2008 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
Disconnect the fuel line to the inlet side of the fuel conditioning module. Install the Fuel Line Adapter 310-159 or equivalent and the vacuum gauge 0-30 in-Hg vacuum. Measure the restriction at wide open throttle (WOT) (maximum engine speed out of gear with the brakes set and the wheels blocked). If restriction is greater than 6 in-Hg, there is a restriction between the fuel pump and the fuel tank. If the restriction is less than 6 in-Hg, inspect both fuel filters. If the filters are OK, install a new fuel conditioning module. Refer to FUEL SYSTEM - GENERAL INFORMATION - GASOLINE AND DIESEL -- F-250-550 (SUPER DUTY PICKUPS) .