did you blow air through the pipe from the egr to the header...those can get cloged...take off the egr so you can see the pintle in the middle...hold a steady vacuum on it and see if it leaks down...that will tell you if the diaphram is leaking causeing it to close up .....also...check your position sensor...only good way to measure that is to put a volt meter on it and do a sweep for resistance.....ie...slowly moving it inward and outward and see if the values are smooth and gradual or if theres a dead spot in it....hope this helps...