Yesterday afternoon I drove the STi to the car wash and on the way it didn't feel right... Like it was losing power. So I stopped in a parking lot and looked under the hood (everything looked fine). So I'm like let me drive it home in case it gets worse. On the way home I get a CEL and read the codes when I got home.
P0171 - System Too Lean (Extreme Fuel Trims)
So I checked over all hoses and connectors (best I could) and then I checked the MAF (connected properly). I removed the MAF and noticed something wrapped around the sensor inside. Looked like maybe some pollen.
Like one of these strings ->
So I removed it/blew it out and used some cleaner. Drove about 25 miles after and so far so far. Not sure how it got through my intake filter (stock intake)...