Just thought I would post my experience with this. I had noticed it, I think, every once in a while the last six months. But it was never that obvious, I always thought I was just seeing things in my rearview. But the other night while plowing it was blatant black smoke, and alot of it. It lasted for 2-3 minutes and then it cleared up. Then it did it again today driving down the highway. Lasted about 1-2 minutes then was clear.
I've always thought I had a DPF problem becuase it Regens all the time. While plowing it's pretty much on the entire time. Over the last few months I've noticed the "Drive to Clean Exhaust Filter" message alot. I started seeing that more than the "cleaning Exhaust Filter" message.
Anyway I figure I have a cracked DPF or maybe a clogged DPF. I'll post up what the dealer says when I bring it in for an oil change. Probably not going to happen for a few weeks.