Isn't that carbon from your exhaust? How old is the actual EXHAUST PIPE that you've got? I've got an old catback that actually came on the car when I bought it... and after I did the engine work it shot that black carbon shizz a good 3 foot strip across the garage floor lol I don't think it's much to worry about... U gotta think there's a fire inside the engine, then it blows the smoke out through that hole ;-) so if u run it a lot, if it has a lot of mileage, etc. I don't think it's a big deal... now if it's like... a brand new catback or something u may have some other probs... just my take on things I may be full of **** lol ;-)