Here's something I came across lately after pulling out my hair
for months on these two codes.

Monitor the cylinder head temperature.

At 186 degrees coolant operating temperature on my 4.6,
My cylinder head temperature reading was at 308 degrees F.

At 265 Degrees, these engines go into fail safe mode and start cutting injectors - Leaning Mixtures, ETC.

This is commonly OVERLOOKED.

Changing the Cylinder Head Temperature switch FINALLY solved my lean codes Problem.

I have also heard of other trucks with a similar problem and they had to have the PCM - Reflashed
because of the computer going screwy and losing it's settings.
.

 

So was your truck going into fail safe mode?

 

Yes my truck had enterered Fail Safe mode after it reached 265 Degrees F. which in turned cut fuel injection on 4 injectors , leaning the cylinders out by 27%.

 

so what year do you have and what was the fix? how did you reflash the pcm?

 

The fuel system monitor does not run once the PCM is in fail-safe mode.

Your "lean" codes were likely generated before the PCM entered fail-safe.

If you'd pulled your freeze-frame data, the CHT/ECT PID would have provided valuable data that would have guided the diagnosis more quickly.