I took my 2008 F250 6.4L diesel to a dealership because it was smoking once it was at about 30 miles an hour after a cold start. They plugged it into the computer trouble reader and the readout showed that there were no problems. The smoke is gray in color and smells like rotten eggs. The truck has 177,000 miles on it and I have never seen a problem like this before with it. Any help would be appreciated.