[shorod]

So the lean codes you're getting are for both banks, and it seems to be related to ambient temperature. The intake manifold gaskets might be more inclined to give you issues on only 1 bank.

I'm suspecting an issue with the MAF sensor assembly. I'd have to check the service manual, but often the MAF sensor assembly also includes the Intake Air Temperature (IAT) sensor. A bad MAF sensor can cause rich and/or lean issues if it's reading the incorrect amount of air entering the engine.

If you a scan tool with datastream mode you might try watching the operation of both the Mass Air Flow and the Intake Air Temperature when things are fine and compare those readings against similar driving conditions at the higher ambient temperatures.

-Rod