[idmetro]

If carbon deposits are the culprit you might be able to lessen them by using a product called Seafoam. With the engine idling you trickle about 1/3 of a can into the brake booster line (so it will get sucked into the intake) then literally dump it in to the point the engine dies (you'll use 1/2 a can or so here) let the engine sit 15 minutes or so reconnect the brake booster line then fire it back up. Pour the reamining Seafoam in the gas tank. It will be tough to start but it will start and then the smoking will begin. It will smoke so much it'll make you think you have a serious internal problem, let the truck warm up a bit and take it for a spin; initially it will sputter and cough but as it runs it will smooth out; in another 15 minutes or so the smoking will go away and I think you will notice a difference. Seafoam is available around here at Napa and Schucks. If you don't like it you're out less than $10....