My 2001 5.4 has a cel p0171 and runs really rough, takes a mile to get up to 50mph.I replaced and torqued all plugs, and coils. I checked all vac lines for leaks. I replaced pcv. tested egr. does any body have any suggestions? I'm gonna check injectors,fuel pressure and fuel filter today. thank you in advance.

 

Check here. Seems the po171 indicates bank #1 lean condition.

OBD-II Trouble Code: P0171 System Too Lean (Bank 1)

Bank 1 is the passenger side.

Tom.

 

check fuel pressure?
when was the fuel filter last changed?
i had the same issues, changed the fuel filter, ran a can of sea foam and its cleaned me up nice and everything is smooth