i have a 02 wrx. it has a Greddy inter cooler, k&n air filter and after market exhaust. i got the car about 7 months ago for the past 2 month a CEL (P0171)(running to lean bank1) had been on. i have change the 02 sensor the fuel/air mix sensor and and the spark plugs. i clean my MAF sensor and air filter and change my gas filter. i check for vacum line leaks and didn't fine any but the CEL keeps coming back on. i had a mechanic check the fuel pressure and he told me every thing is ok he doesnt know why the CEL is on. according to him the light should not be on every thing is working the way it should. the car runs great. if i clear the CEL it comes back between 20-30 miles after clearing it. can someone please help me or should i just send it to subaru.