Hyundai Repair: 2001 Hyundai XG300, air flow sensor, gasket leaks

Question
I have a 2001 Hyundai XG300 that keeps coming up with the codes PO171 and 174, I just got the fuel pum and fuel filter fixed yesterday but by the end of the day my check engine came on. So i went to get it put on the machine and its still reading the same codes.  What could it be?

Answer
It could be many things.  Basically, these codes simply mean that the computer must keep the injectors open much longer than expected in order to achieve the proper readings from the oxygen sensors.  

If you're looking to take a guess, the short answer is that it's probably a defective air flow sensor.

But keep in mind that it could also be any of the following:
-- vacuum leak
-- excessive alcohol (methanol) in fuel
-- break in bellows between air flow sensor and throttle body
-- bellows loose at either air flow sensor or throttle body.

We can eliminate oxygen sensor issues and intake manifold gasket leaks as these would tend to cause only one bank to be excessively lean.  The fact that you have P0171 and P0174 tells me that both banks are lean (or at least perceived to be lean).