Ford 4.6L Engine and P0401 Insufficeint EGR Flow

The P0401 code refers to not enough flow of the EGR system. Most common problem for the Ford 4.6L engine, is the flow ports in the throttle housing. If you have this code, try this procedure first, before spending any money.
First remove the two EGR valve mounting bolts. Leave the pipe connection connected to the valve, then remove the air intake tube to the throttle housing. Next remove the throttle housing from the intake by taking out the screws that hold it in place, and disconnect the throttle linkage.
Remove the housing and turn it over, look at the ports (holes) for the EGR valve, they will most likely be covered with carbon crud. Clean these ports out completely, reinstall the housing and tighten all the bolts, reinstall the linkage and air intake tube. Clear the code with a reader, and test.