Yeah second the O2 sensors. I got lean codes for banks 1 and 2. This was after I submerged the motor however.

How hard was changing the O2 sensors?

 

For driver side front I had to remove the front driveshaft. Besides that it's easy.

 

Very true, not very difficult.
22mm and just hope that none of the threads strip.
This happened to me with the drivers side sensor before the cat.
While I was removing the OG o2 sensor, the thread broke on the o2 sensor and damaged the thread. Truck does seem to run much better.. and a tad bit higher mpg too boot.