black dust?

hey y'all, i have a 99 durango, and i've notice lately that there is black residue inside the exhaust pipes. it looks like brake dust, but is really black, something like the coal you use on a barbecue grill. the suv in not throwing any black smoke or anything. is it normal or is something going wrong in it? any suggestions would really be appreciated. thank you.

You're running rich.

its called carbon.completely normal.