[makdamit]

if and i say if the heads are warped but still hold a seal to the lower block the knock sensor can get a read at low rpms thats false and the on bord computer or ECM can clock it out wrong. thats a one and a lifetime fix ive seen. The driver side head was way out and the cam was a little wonky. The other more common thing ive seen is the spark plug fix kit was instaled at an out of spec depth making some odd work of the combustion chamber. But the way to detecting this is a full dyno read out form a tech that really knows fords. Its about 100 to 400 bucks but it will tell you everything about your engine and is downloaded to a thumb drive for you to keep. what I would suggest over all that is an engine swap to a crate keep the old core and rebuild it or have it rebuilt. its about 1200 plus 200 or so core charge. If you keep the core bothe engines cost you about 700 bucks a peice and you already know the status of the old one and the new one has a warrenty. the motor pool for the U.S ARMY always dose this swap insted of reparing a core. General mechanic, welder/fitter, millwrite of 20 years. have a great day all, and best of luck bud.