Like others have stated could be a dirty egr which isnt that hard to clean if you know what you're doing. Since nobody has said this I will, if the truck hasnt been started in months, if you buy it, I would really clean out that turbo. chances are that the turbo veins could be stuck causing it to smoke a little bit more than usual. But I do know that if a turbo powered truck sits for long periods of time, the turbo tends to stick and wont function to its potential. But a headgasket, stud, and cooler job if done yourself should be like 2-3k bucks. I think....