easy fix guys; Go to the dealership and purchase a DPFE sensor (Delta Pressure Feedback Sensor) The EGR valve rarely fails it usually is a failed DPFE sensor, the DPFE does not directly talk to the computer like EGR does so if the DPFE fails it causes irregular reading at the EGR thus the engine code and poor gas mileage/ performance. Ford has actually released a Technical Service bulletin stating that the DPFE sensor can and will fail prematurely. so in a hundred words or less if your receiving a code that says insufficient flow or overflow replace DPFE sensor takes 5minutes to fix. | 
