95 mercury grand marquis 4.6 100/000 miles

First take the egr valve off the car, then clean the small orifice out right thru to the throttle body, I use a coathanger. Put it back torether and get the light turned off, Autozone will do it free, just ask them to check the codes, the egr code will still be in there. Tell them to shut off the light, if it stay off you got it right. This is a very common problem with fords.
If the light comes back for the same code replace the egr position sensor.