P0171/P0174 codes L300 V6

"Mixture too lean" both banks 1 & 2.

This code kicked in when going up a steep hill in the mountains.

Added can of fuel injector cleaner to gas tank - any other suggestions?

 

According to http://www.obd-codes.com/trouble_codes/generic/p0174.php ,
possible solutions include:

a.. In the vast majority of cases, simply cleaning the MAF sensor does the
trick. Consult your service manual for it's location if you need help. I
find it's best to take it off and spray it with electronics cleaner or brake
cleaner. Make sure you are careful not to damage the MAF sensor, and make
sure it's dry before reinstalling
b.. Inspect all vacuum and PCV hoses, replace if necessary
c.. Check for a dirty fuel filter and proper fuel pressure