Ford Repair: engine missing, o2 sensors, liter engines

Question
I had my 2001 f150 4.2 liter diagnosed i have replaced right front oxygen sensor egr sensor and egr valve all within one week service light is back on and now it says egr flow is excessive and bank one and bank two are lean I'm just a regular working guy trying to save money by fixing my truck myself and i feel like I'm running in circles wasting money instead of saving it can you help me your advice would be greatly appreciated

Answer
hey there.  changing O2 sensors and egr valve is not going to change the engine running lean condition unfortunatly. Are these lean codes stored in the PCM??? A lean code usualy indicates a vacuum leak somewhere. And on these 4.2 liter engines a possible IMRC inopperative. (Intake manifold Runer control) the rods for the IMRC are located in the rear of the engine and requirs a mirror to inspect all 4 clips. IF you have any other questions do not hesitate to ask. good luck
Chris P