This is pretty hard to believe. Sounds like the stuff of urban legend. Would somebody REALLY spend the money to do this?
HuffPo has a story on it.
http://www.huffingtonpost.com/2014/07/06/rolling-coal-photos-video_n_5561477.html
Negative.
You can purchase fuel management software that will make a diesel pickup blow black smoke in quantities that would make a steam engine blush.
Not that there's anything wrong with that.
Think hot rods modified with tanks and plumbing to "shoot flames" out of the exhaust. Very popular with some of the "second childhood" set. I stopped by my local post office, and two guys (old farts about my age) had the hood up on a Chevelle 427 (obviously lovingly restored) with the mod.
OH Yeah!
Just go to YouTube and search for coal rolling... There are some really, really funny videos there! And as a bonus, you get to read the squealing comments from the nancy boys, makes your heart go pitty-pat! Not all men drive diesel trucks, but all diesel trucks are driven by men.