p0171 and p0174
 

my mom has a 2008 GT/CS it is completely stock she babies it when she drives it. it has 20k miles on it. she had a check engine light on so we ran the codes and it came up with p0171 and p0174 codes(bank 1 and 2 running lean). she said the air filter hasn't been changed on it so i took a look at it and it was pretty dirty. i reset the codes, then shook it out and got what i could off of it told her to go to autozone and buy another one. would this cause these codes to come on? i looked around what i could see and didn't see any loose vacuum lines.