I have a 2004 f150 5.4L. Pulling RV home from FL I lost power engine light came on. Code p0191, p0171, p0174. It was a Friday afternoon went to ford dealer they seed it looked ok on computer that it mite be fuel pump. Left RV in FL. Came home to my ford dealer they cat find a problem. I change fuel filter. Went back for RV 166mi into trip home lost power. Codes p0171, p0191. Looking for help.

 

Two codes are telling you it's a lean condition both banks (as expected).
One code is telling you of electrical type failure.
Since it takes a long interval to show, you have to make a decision as what to do next.
If the fuel pump is failing either put a pressure gage on so it can be monitored at he time of failure, change the pump or relay if there is one.
It's pretty well defined as to what is causing the loss of power.
The codes are the key. The 171 and 174 codes are the end result of the code 191 "failure".

 

I got a tank of bad gas while pulling my trailer. I could not do over 30 mph. I stopped at the next station and added 2 cans of dry gas plus a can of injector cleaner.
I let it idle for 15 min and it keep running better. It ran perfect for 600 miles till I parked on a very steep driveway and had to do it all over again........3 K later all OK......

 

Its not a good thing to go lean, especially pulling a heavy load...