hi everybody. i'm new to this. i have had my 2000 dodge dakota qc 4x4 for a year and a half now. everything was awesome till recently. it has the notorious 4.7 v8. it started throwing codes left and right for the past 2k miles. the code was p0171 lean on left bank. i changed the o2 sensor on that side. the upper and the lower. it still ran like crap and was throwing black smoke. i took it to vip and they said motor had blown head gasket and no one would fix it. i bought the gaskets and changed them. once in there, they looked good and there was no sign of leak. plugs were definitely bad. we put it back together and it still threw the code p0171. i read up on it a little bit and decided i better change the o2 sensor again. it came right out of it for the first 200 miles. i stepped on it one day and it threw the p0171 code again. some one please help if you can