my cars check engine light came up and gave me two codes they are p0171 and p0174 system to lean. i cannot find the problem. i checke the vacuum lines, maf sensor, changed the spark plugs, and change the 2 upper o2 sensors and the codes still appears. i also noticed the blowers bolts were loose for some reason. i bolted it down and im still getting the same check engine codes. i was wondering if any of you know what the problem may be.