I had same problem.
replaced EGR....no help
replaced EGR selinoid no help
it ended up being the EGR DPFS
"EGR Differential Pressure Fedback Sensor"
its a rectangular metal box with two hoses hooked to it mounted under the EGR...kind of difficult to get to.
the replacement par was like $50-$60...plastic of course..installed it and haven't had a problem since.
hope this helps
