the MAF failed before i had it tuned. p0171 and p0174 IIRC were the two being set. was watching it on the tech 2 at work and unplugged the MAF and long term trims went to 2%. with there still being a junk MAF in my car for now just for the air temp sensor i'm not replacing it. i replace alot of MAF's that go out and don't feel like wasting money on one.