they say they won't take the part back once installed 0.o wth!
Chain stores are driven by the benjamins; they want your money period. NAPA and Carquest are normally locally owned so they take better care of their customers. Plus (at least in my town) NAPA and Carquest have a couple little trucks to run parts to the mechanics in town. So the mechanics shop there.
Let's look at Code P0102. The PCM sends a voltage to the MAF on the signal circuit (one of the four wires). The MAF uses the voltage in order to produce a frequency based on inlet air flow through the sensor bore. The frequency varies within a range of around 2000 Hertz at idle to about 10,000 Hertz at maximum engine load. P0102 sets if the PCM detects a frequency lower than the possible range of a properly operating MAF sensor.
Start by inspecting for the following conditions:
1. A restricted air intake duct
2. A collasped air intake duct
3. A dirty air filter element
4. Any objects blocking the air inlet screen of the MAF sensor
5. Any debris on the sensing elements of the MAF sensor
6. Any vacuum leak downstream of the MAF sensor
7. A MAF sensor that is installed backwards
8. A restricted exhaust system
A low minimum air rate through the sensor bore may cause P0102 to set during idle or during deceleration. Inspect for vacuum leaks downstream of the MAF sensor. The conditions required to set code P0102 are:
1. The engine cranking for 0.5 second or running 1 second.
2. The engine speed is more than 50 RPM.
3. The ignition 1 signal is more than 8 volts (battery isn't dead)
4. The idle air control (IAC) position is more than 5 counts.
5. The above conditions are met for more than 0.5 seconds.
So as you can see it doesn't take much for this code to set.
anyway to check the maf sensor to see if it's bad
In order to check the MAF sensor you need some way to watch the output and see if its linear. On my car I got the following readings:
0 RPM = 0.21 LB/M
950 RPM + 0.91 LB/M
1150 RPM = 1.36 LB/M
2086 RPM = 2.06 LB/M
If it were me my next step would be to get some MAF cleaner (Yes they make it, Advance Auto carries it) and clean the MAF up real good and reset the code again. Check the condition of the wiring harness making sure there is a good connection on all four wires.