Working on my friends 2005 Ford Ranger 3.0L v6, I need some second opinions

02 sensors can definitely cause it to be lean and would throw the banks one and two codes. If I were you I would replace those before sending off the fuel injectors, as it would be a much cheaper potential fix.

Clean or replace Mass Airflow Sensor. Will be just downstream from air filter housing.

Thank you for the reply. I'll look into it.
I will consider this. Thank you.
I mentioned in my first post that I already replaced the MAF with no prevail.

but, would it affect performance, is the thing. For some reason my memory is telling me it can affect it and cause it to misfire, but unknown. These codes are probably thrown from one single issue.

I'm not going to reply on the shop's word anymore and going to check the basics, because it seems to be right under my nose.