SES came one with codes P0174??

[pathfinder9035]

i know theres been past forums about this but my problem seems to be a little drifferent ok so it all started awhile back ago when i changed my spark plugs and my number 2 coil went bad because i forgot to plug it in when i started the car. well i replace the faulty coil pack and now its running great. but before i repaired it i was driving the pathfinder for 3 days with the engine misfiring horribly cuz ihad no choice and i needed a way to get to school. So after i fixed it i took it to advance the other day to reset the codes since now its running great and i wanted to reset it. well i did and i drove it for about 100 miles and the check engine came back on again. this time with 2 codes, p0174 meaning system to lean bank number 2 and 1. the truck is running normal with no hesittation or anything no pinging or knocks it drives beautifully no change in mpg i mean i drove to penn state today to pick up my gf and still manage 19-20 mpg doing 80 which is normal for me (heard about those symtoms from forums in the past about the same problem). what could have caused these codes to show up. what is it that i need to fix for these codes to go away. is my maf dirty?? my cats bad?? my o2 sensors bad??.. i did drive the car when it was misfiring in cylinder number 2. was gas dumped into the cat and messed it up since it wasn't firing. this truck only has 104000 miles and i need it to pass inspection in december. student in need of help

Modified by pathfinder9035 at 11:31 PM 10/10/2008

Modified by pathfinder9035 at 11:32 PM 10/10/2008
Modified by pathfinder9035 at 11:35 PM 10/10/2008