P0171 code

P0171 Adaptive Fuel Trim Too Lean (Bank 1)

* Vehicle driven low on fuel or until it ran out of fuel * One or more injectors restricted or pressure regulator has failed * Fuel delivery system supplying too much or too little fuel during cruise or idle periods (e.g., faulty fuel pump, or dirty fuel filter) * Air leaks after the MAF sensor, or air leaks in the PCV system * Air leaks at the EGR gasket, or at the EGR valve diaphragm * Exhaust leaks before or near where the front HO2S is mounted * HO2S is contaminated, deteriorated or it has failed * Fuel control sensor is out of calibration (i.e., ECT, IAT or MAP) * Base engine "mechanical" fault affecting one or more cylinders

My check engine light came on at the last AutoX. My OBDII reader gives me the P0171 code. The pointy board mentions the above list.
Car runs and drives with no noticeable change (99 with CAI, JR header & midpipe, roadster sport exhaust, 120k miles)

Any thoughts on where to start? I'm thinking to start with the fuel filter, as it's probably the original.

Can you clean the MAF on NB's? I forget. If so, try that.

Thanks Sammm! That was the easiest, cheapest fix to date! CRC took care of it.

Well, I did by a Harbor Freight OBDII reader, but I'm not including that. If anyone needs to borrow a reader, it's available...