hey guys went and got gas tonight and went to walmart. when we came out started the truck to leave and soon as i put it in drive the service light came on. we took it to autozone to use their free scanner and it said 3 codes 171 and 174 twice. the print out they gave me says lean bank on one and two and MAF sensor. hasn't anyone else had this trouble?? its a 2002 tahoe 5.3 vortec flex fuel. i called the local autozone and they have one sensor instock for $80 with a $60 core with a year warranty. my question is should i go buy the new sensor and try it or take it to the shop and see what they have to say???