P0171 code problem

I know all of the possible problems that can be associated with this problem, but most of them would cause the car to miss or sputter and my car is not doing that. I don't wanna buy a part and then have wasted money cause it didnt need it....any ideas? could it be that i need a new fuel filter? and if it is the fuel filter anyone know where the filter is located on the 4 door automatic 2005 model?

Suspect bad plastic, rubber seals, or gasket!
Need to check the EGR,PCV, and Inake system for unmetered air leaks.
I would do a smoke test, befor throwing any parts at it.