I had the same problem with poor gas mileage and a CEL. I ran the OBD-2 software and I had a P1518 code. That is the IMRC (Intake Manifold Runner Control) module cable had broken so the secondary ports were stuck open. Unfortunately, the part from Ford was about $150. I would check if Motorcraft makes the part, then you could get it from NAPA or similar parts store. Hope this helps.
