I have had this checked out many times and have replaced all 4 02 sensors but can not get code to go away. Sometimes it tells me 02 then it says mass airflow. Same two codes but no one can fix this. Ford house or private shop. It runs a little rough at idle and gas milege is down. This is a v-6 with dual pipes.

 

You should check your vacuum lines. I had the same problem in mine. For me it was the vacuum line connected to the PCV valve. You follow the line to the very back and there is an elbow attachment. For me it was the elbow that had a big hole in it. I replaced it for like $8 and now my truck idles correctly.