Why does the 'check engine' light keep coming on?

Lean Bank #1 and Bank #2, Check For UnMetered Air

It means one of two things. If the code showed up while driving at speed, it may be a fuel delivery problem. If the code showed up while idling, it is probably a vacuum leak of some kind. Look at the freeze frame data of the codes to figure out which direction you need to go. The easiest thing to do would be to inspect and smoke the intake (cigar or smoke machine) to find a vacuum leak.