Sounds like MAF, the air intake boot has fallen off the throttle body or a huge vacuum leak.

Did you check your oil when you filled up? The dip stick is behind the air intake boot. It's possible you knocked it off checking the oil.

The "too lean" means a intake/vacuum leak after the MAF and before the O2 sensors. For it to be on both banks narrows it down to between the MAF and the intake.

The MAF knows how much air is going in and it tells the computer how much gas to put into the mixture. The O2 sensors confirm what is going on. If more air is going in than the MAF is saying the O2 sensors pick up a lean mixture. For both banks to be lean it has to be something that both banks have in common. . .MAF, air boot or vacuum leak. Additionally, the MAF would set it's own code.

__________________
0O(llll)(llll)O0
2007 Suzuki Vinson 500 4X4
2007 Toro 6.5hp
2006 BMW X5 4.4 ltr (his)
2001 BMW X5 4.4 ltr (hers)
1994 Honda XR650L
1984 Honda XR80

"Beer is proof that God loves us and wants us to be happy."
Benjamin Franklin