Smoke question

My truck has a smoking issues, the smoke is white/blue in color.
When I start up my truck I get a little puff of that color smoke, while it is idling in park the smoke continues, and if I rev the motor up I get a good shot of the smoke. But while I'm driving, it doesn't seem to smoke at all, just when idling, or if I'm at a red light I can see a little.
The truck has new injectors, return lines, and glow plugs as of the previous winter. Fuel filter was changed last week. It smoked the same before that. The IP I don't believe has ever been changed (has 108k). The truck does not consume any oil, or antifreeze. But once and a while I get the "engine temp" light come on for a minute or two, maybe a couple times a month. Maybe that and the smoking are related? When that light comes on, the truck is running the same, and the regular temperature gauge on the dash reads normal (I know the stock ones are crap).
The weird thing is, I started putting additive in the truck at ever fill up, and the smoking pretty much went completely away, for a few months. Then I stopped using additive just to see, and the smoking came right back.
Thanks for reading :thumbsup:
:ford:1994 f250
Idi non turbo
Regular cab
4x4 E4OD