P0171 & P0174 usually means you have a bad MAF, defective O2 sensor, misfire, or fuel injector problem. try cleaning the MAF with non chlorinated brake parts cleaner. Next change your spark plugs if you don't know how old they are, you can remove and re-gap and replace with the same ones if they don't look to bad the gap is .052-.056. If your lucky you know somebody with real time scanner that can monitor your O2 sensors to make sure they are working properly Look at the MAF output at the same time and if either the O2 or MAF don't look right replace them. If all of that doesn't help you might consider having a professional fuel injector cleaning at a shop usually 75-100 bucks.
