i drive a 2010 GMC sierra 1500 and its been throwing p0171 and po174 codes I did a smoke test on the vacuum lines and on the exhaust and no leaks
it runs a little rough and I don't seem to notice any loss of power and it'* not misfiring
I recently replaced the fuel pump and the maf sensor so I don't think it that

does anybody know what it could be??

May I ask why did you change the fuel pump and MAF? I am asking because those are two thing that can cause those codes to happen? If you were trying to fix the issue with changing those parts what brands were used? Did you try running cleaner through your tank first? Next I would look at fuel filter (test and make sure fuel pressure is at 50psi).

If you're not getting he correct pressure then something is wrong with the pump. Also check air your MAF to make sure there are no clams loose letting air get in where it is not suppose to

Which engine?

Also spray top of engine with carb cleaner looking for an increase in rpm, indicating an intake leak...

How many miles on it?

Where does it live?

Does it do this more when the outside air temperature is cold?

My first guess would be intake manifold gaskets.

Do you have a scanner that shows live data. Knowing what your fuel trims are at various RPMs can help with diagnosis. Search Youtube for Fuel trim theory and the codes that you mentioned.