2000 f150 v-6

My check engine light on. I had the codes read ay autozone and are as follows.
PO171 fuel to lean bank 1
PO174 fuel to lean bank 2
I have changed the egr valve appx. 1 year ago after a PO402 code (excessive flow)
I have checked all vacumn lines and replaced the pvc valve once already and would apprecate any advice.
The engine pings at times and I notice that the rpms somtimes increase at idle from 900 to about 1200rpms.
Other than that it runs great.

Thanks in advance!

1) Do a smoke test for unmetered air from EGR, PCV,and Air intake system.
2) Did you clean the Massive Air Flow(MAF) with CRC MAF sensor cleaner.
3) Replace upstream H02 sensor.

1) yes
2) Good possibility
3) Probably not the problem. More than likely if it is not the MAF, it will be a vacuum leak.