pageparsley: The two parts that may the culprit & I would be willing to bet real money that it is one of these two parts if not both, the delta pressure feedback sensor [dpfe] sensor ford part
# is f63z9j459aa, and the sensor relay is ford part # f77z9j460ab
both of these parts work in sync to provide correct egr flow &
smooth vehicle operation, the dpfe sensor will not cause noticeable operation problems you should just get a check engine light, now on the the hand if the relay is the culprit you will probaly notice some vehicle surging at around 40mph up to 55mph this could be described as a backwards to forewards
motion of the vehicle. From experience if the relay is at fault it
would be wise to replace both sensor & relay[ I mean its like you
would not change your oil without changeing your oil filter] , if it is just the sensor you have a good chance that may be all you need replace. If you run into any problems tell us.
turbo ted