People who purposefully make their diesel truck engines blow out thicker, blacker smoke are either idiots or just don't want to be friends with anyone who might encounter them on the road. Or both, amirite?
I say idiots because if they think blowing more smoke means more power, it doesn't. It's just a waste of fuel and is nothing but a cry for attention. Just like racing strips and spoilers on Honda Civics.
I say nobody wants to be their friend because anyone who's attitude is, "fuck yall even if i don't know ya... could be a sweet old lady.. who cares?? Eat muh smoke!! Yee haw!" is not a desirable quality of a friend. Even with the benefit of the doubt that maybe they just don't realize they're creating a hazardous smoke screen on the road behind them, they're still oblivious idiots.