Lean Bank1, Bank2

[bonasa]

HI All, 2008 5.4 3v 165k miles. Immediately after a fill up I lost power and 171/174 codes popped up. I figured bad gas, ran it out with a can of sea Foam, re filled with Mobil Premium-no change, same codes

To date have replaced the fuel filter (was dirty) MAF( slightly off numbers), cleaned and re oiled KN Air filter, new pcv valve(Old stuck open). Have propane tested for vacuum leak-nothing. Sometimes I will get 150 miles of full power-still horrible mileage, then the rough idling and no power and CEL with same codes. I am stumped. Any thoughts?

 

[Plati]

My 2003XLT had a P0171 P0174 and I had the common problem to cause this of the PCV elbow.
See--> https://www.expeditionforum.com/threads/obdii-reader.34543/#post-288245
it was an easy & inexpensive fix

of course you said you checked for vacuum leaks … so ?