While rolling coal is dumb, what about diesels that are modified for economy? My own diesel is set up this way and will only give a small puff of smoke when suddenly accelerating like on an entrance ramp to the interstate or passing a slow vehicle on the highway. Would I be fined if I passed a car and the wisp of smoke from my truck touched their car? These modifications get me an extra 4 mpg and when you drive 20,000+ miles a year like I do, that saves over 300 gallons of fuel, and $1,000+ in fuel cost. [spoiler]And no, I don't drive a big truck for no reason. It's a work truck that is off road during work hours, and haul my travel trailer I live out of on the road.[/spoiler]