We have had the truck "Smoked" twice and found the intake gaskets and Fuel Regulator leaking so we replaced the following so far.
Upper and Lower intake gaskets and valve cover gaskets (Victor Reinz found out that was who Ford recommended since they do not make all the parts anymore.)
Throttle Position Sensor and Mass Air Flow sensor
All three O2 sensors twice
PCV Valve and hose
We have checked for vacuum leaks by spraying mass air flow cleaner and brake cleaner nothing happened.
However, the Short Term Fuel Trim is from 0 to 11% and the Long Term Fuel Trim is at 25%.
We have a small but effective scan tool to give us those readings and we have disconnected the battery for 4 hours and reconnected and drove it 200 miles in town and highway and still have the codes and the fuel mileage is not great at 18 mpg but, we do not have hesitation nor rough idle so, my son and I are a little upset and it has to pass an emissions test to get inspected and it will not at this time. Can you help?
The code states the oxygen sensors are detecting a lean air/fuel mixture. The best way to check for leaks is with a smoke leak detector machine. You may or may not have access to this tool? I use starting fluid spray to quickly check for leaks within the intake system. Now take your time (your scan tool my have a slow sample rate) to spray the intake sides (each bank) around each injector, the plastic intake itself and anywhere from the behind the mass air flow sensor to the engine intake ports. Inspect the intake tube for any openings. Any air getting sucked in after the mass air flow sensor is air not accounted for by the mass air flow sensor so the o2 sensor will notice more oxygen content than what mass air sensor is registering. Check the short term fuel trims (both banks) when spraying for leaks.
The pcv/vent rubber elbows like to collapse internally so inspected them by removing and looking on the inside.
Let me know if this answered your question or if you have any other questions. Talk to you soon, Ty