White smoke
White smoke is usually due to coolant in the exhaust stream - ie steam. It may be a small leak right now, and not much coolant accumulates in the intake until it has been sitting a while. You can pull the EGR valve and see if it is shiny (wet). sometimes if the coolant system is pressurized and the back end is raised, you can see moisture inside the hole where the EGR valve sits.
If you want to get under the truck after it has cooled, you can look at the clamp that connects the exhaust Ypipe to the EGR cooler. It is at the back of the engine, near the top, just below the intake manifold. If you see moisture on that clamp, you have a leaking EGR cooler.
Bama - if you've been through a bunch of EGR coolers, you might suspect a leaking head gasket overpressurizing the coolant system, should'nt have gone through that many coolers!
