My check engine has been on for a while and now I need to get it smogged. I pulled the codes on it and it brings up lean bank 1 and lean bank 2. I talked to a friend of mine that is somewhat of a car buff and he said to change the cap, rotor, and wires. If that dosen't clear it, he said to clean the MAF Sensor (that didn't work). All the sudden he dosen't know.

Any suggestions?