Fuel bank leans
 

Ive posted about this before but I still cannot figure it out...On my Chevrolet Silverado 2500HD my check engine light comes on and off and when it is on it reads leans on both of my fuel banks. Sometimes when I start it, it has a rough idle until it warms up a little. Now, it seems to only do this in the cold weather but if I keep the tank filled up while its cold the light does not seem to come on. It has been recently warm and it hasn't came on for a while. Anybody have any ideas? I cannot for the life of me figure it out.