Hey i have 69 camaro,i have done an overhall on the engine about a year ago. For a few months now i have noticed black smugges on the back of my car right above the exhaust pipes and a real light mist of black all over the back of the whole car. I can only get it off with degreaser. I don't know if my car is just running too rich or what. I could use some help. Thanks for your comments!