CE codes P0171 and P0174

I'm getting these two codes
P0171-system to lean Bank1
P0174 -system to lean Bank 2
Its a 98 expedition ,sometimes it's very hard to start,and its like running not on all cylinders.
Please help.

The trucks I've seen with those codes alot of times have been the PCV valve and/or a dirty MAF. Replace the PCV valve and check the hoses and spray the MAF with Electrical Contact cleaner that is marked No residue!!

i'm getting the same codes, mostly the PO171, at random intervals, presently no CEL, but running somewhat rough under mild to heavy acceleration, feels like it want's to smooth out, but just can't quite get there.
the PCV valve assemby all the way back to the rear of the intake manifold was replaced just over a year ago, going to run some fuel system cleaner through it today, while towing a 5k travel trailer, should be interesting!
wish me luck!
Rick, Ore