My 96 F150 XL with 4.9L recently failed state inspection due to check engine light and P codes. Tests found leaking EGR and IAC valve bodies, also that CAT was burned out. Replaced both valves and CAT, cleared codes, drive truck till all monitors were READY. Truck passed state insspection and ran code free for about a week, that's when the check engine light came back on and the bank 1 lean code has returned. HELP?