2001 Ford Explorer EGR excessive flow

Most of the time this is a false indication, due to a bad DPFE sensor. No way to tell for sure unless the system is tested. There are other possibilities, from disconnected tubes to a clogged EGR valve, to a bad solenoid. All these parts are inexpensive. Probably an hour of labor to diagnose and replace a failed part, at most. I wouldn't expect to pay more than $150, hopefully less. If you are a gambler and not afraid of bruising a knuckle, replace the DPFE yourself and see what happens. Nothing more than a small wrench (can't recall the size) needed.