I have soot on my '08. I don't think its anything bad after all you are burning fuel, its just the design of the exhaust shows it a bit more. Go stick your finger in your tailpipe on your car and it will come out a bit sooty, its just usually on a car you have a tip that sticks out and that's it and on the Connie, that tip sits insides of the outer cap which gives the soot a place to build up visibly and having it silver just makes it show more.