I have been dealing with the P0171 code in my 04 WRX for the last couple weeks and am going crazy. I have checked for leaks, replaced the turbo inlet, PCV valve, spark plugs, fuel filter, ran injector cleaner, replaced front 02 sensor, replaced the MAF sensor, cleaned the IACV and replaced the gasket, and replaced the air filter. The only mods on the car are a catback exhaust and catless uppipe. I have even taken the car to the dealership and they were basically clueless. The car is a 4eat and the CEL comes on between 12-15 miles of driving after a reset everytime and at cold start-up the idle is very lumpy for like a couple seconds. This CEL is driving me crazy.