Hello all,
I have a 99 Expedition with a 5.4 liter which has 80000+ miles
on it.
I recently battled EGR codes for the past few months along with
a bucking/miss in the engine at around 35 mph driving.

I started off by replacing the EGR valve, then cleaning
the throttle body, replacing the plugs and fuel filter
but nothing seemed to help. Then I found this web site
and somebody posted that 9 out of 10 times EGR problems
are caused by the EGR position sensor.
So I bought a Soranson from Advanced Auto for $51 and BINGO, everything is fixed, including the bucking in the engine.

I thought I'd let folks know in case they have similar problems.
Start with the darn position sensor.

thanks everybody!