We had to replace the EGR valve on ours. When ours went, it ran very rough whenever you took your foot off of the gas to slow down. It ran fine when we were driving at highway speed. Dave had to two-foot it all the way from Indiana to Ontario!
We had taken it to a dealership in Indiana and he tried to tell us that the cam had shifted!
There's a thread on PTCrew right now about replacing EGR valves, and it includes pics.