It is possible that the 'pintle valve' on the 3.9V6 version is smaller to limit EGR flow at mid throttle.
There is also a nearby 'EGR Modulating Valve' that pulses the vacuum to the actual EGR valve to control the amount of flow. This EGR Modulating Valve also has an exhaust backpressure port meant to keep the EGR flow off until you get to mid throttle power levels.
The EGR is turned off at idle,
and at wide open throttle
... it is used in the middle throttle positions to cool peak combustion temperatures and limit NOx pollution emissions
I have cleaned out the cast-in-place EGR passage inside the aluminum intake manifold by
first packing and turning off the truck on a hill with the front of the truck highest up the grade,
then using a long plastic tube and spraying Chrysler Combustion Chamber cleaner into the two sideways holes underneath the throttle body blades, letting the solvent flow back down the passages and hopefully begin loosening the carbon deposits,
waiting 20 minutes to let the solvent do its work,
then starting the truck up
and watching the black smoke cloud come out the tailpipe.
The steel tube from the exhaust manifold up to the bottom of the EGR valve can also become plugged.
If the spark plugs are in good shape,
EGR is supposed to slightly improve MPG at highway cruise.
If the spark plugs and ignition system is not in tip top shape,
EGR can make mis-fires more likely,
and can hurt MPG with each mis-fire.
The EGR valve for a 1995 5.9 V8 was $134 at the dealership about 8 years ago.
