PO171 system too lean (bank 1)

[6waystillsunday]

I was driving home from the mountain today and noticed a CEL. Turned off the car plugged in my AP and found this code. I read a few posts that talked about this and what to do, But I just wanted a better opinion with the mods of my car, miles ect.

05 wrx 27,000 miles
Mods include:
Aps cai
Aps turbo back
Cobb AP Stage 2.

I reflashed the ecu to see if the code comes back on. And if it does what should I do?

Thanks for your time.

[SD_GR]

Check for vacuum leaks.
Replace the factory air intake and make sure it's seated and seals correctly.
Clean the MAF.
Check the vacuum connection to the fuel pressure regulator.
If all else fails, assume the CEL is actually correct and check the O2 sensor.

[6waystillsunday]

What is good to clean a maf sensor? I work at a dealer and have access to most zep products along with parts wash.

[SD_GR]

There's a dedicated MAF cleaner product made by a company I think is named CRC or something to that effect. It's in a gray/white can. I think Big Sky WRX made a "clean your MAF" thread a while back, and the product was pictured (search). Since the MAF is more of a sensitive electronic part than it is a car part, I'd only use something you know will not harm the sensor.

[6waystillsunday]

alright, Thank you for your help.

[TrackReady]

a P0171 is normally a vacuum leak or a misfire. I would say that less than 5% of the time this code comes from a faulty o2 sensor. Check around for cracked/ loose vac lines. You could also have a misfire, although about half the time you will also get a coded misfire code (P03XX.)