There was a TSB on the EGR valves, and the older valves had a tendency to stick, so it might be a good idea to install a new one.
Additionaly, the hot inlet pipe to the intake manifold gets clogged up with carbon from the egr vapors. >>
Just to add to Paul and Engs excellent info:
As both of these are troublesome CE/code #5 trippers , There is a difference in the diagnosis/complaint..
The pipe blockage decreases the egr air flow , while the egr valve [ sticking open] does not shut air flow off [mostly at idle].
One can usually tell which one [ short of pulling hand vac to egr test ] by observing the engine idle.
The egr sticking will show an intermittant rough idle...
where-as, the blockage will not show any driver complaint
except the CE lamp.
I do have the TSB info on the EGR valve change, if needed
[ email me for a jpg]