P1401 - Differential press feedback EGR circuit high input.
to me it doesn't seem to serious, you feel a affect in performance at all? what other codes have come up? never dealt with this code before on my 01 so hope someone else can elborate on the code, good luck.
Its located to the right rear of the intake manifold right in back of the fuel pressure regulator. The sensor should be aluminum(boxed shaped) with one connector and two hoses attached to the bottom of it that come off of the EGR tube.
They are not cheap, Ford really sticks it to people for these cheap ass sensors, I think they are around $75.