Engine code 171 sys too lean bank 2

[Sfusmc1]

When in overdrive on highway I am losing power when trying to excellerate and engine light starts to blink. It also happens when going up hills too fast. Was informed the the code was 171 sys too lean bank 2. I have replaced OS on previous vehicles but this symtom is different. My engine is a 2005 5.4. ANy help?

 

[svtfiveoh]

I had the same problem on my 03 5.4 ... My issue end up being a Mass air flow meter. I replaced it and so far no problem.