I live in Colorado, and on cool mornings, 30 degrees and below, my LLY 2500 GMC constantly smokes. This is only on first start up and once the truck reaches about 150 degrees it stops. I have taken it to the dealership, but they said it was a dirty air cleaner. Air cleaner change, no help. Any ideas?

Interested myself, as my fathers 01 lb7 does the same thing? Maybe Normal.