well i did some thinking your check engine light would be on if it was an o2.... see how the b12 works and if it dose.. good its the fuel injectors or filter... if not it may be a head issue with a leaky oil seal. their may be oil leaking into the cylinder when its off and when it reaches its burning temp it sputters and burns off then runs OK.. double tap checking the plugs for oil and dark black.... other possibles next oil change let it set check for coolent, and if a buddy has one do a leak down or pressure check on each cylinder
inspect all of the vacume lines with a fine tooth comb. we will just do simple until i can get a better feel for the truck
