Iam not familiar with Ohio , would make sure its operating properly, My 109 doesn't smoke at all even under load. But at the risk of POLITICAL INCORECTNESS, Is the smoke measurable . is it Illegal in Ohio in the time it will take you to discover the culprit. If its illegal , certainly don't drive it . All for environment , BUT one M 35 is not the end of the world. Far more pollutants are added to the atmosphere invisible and silent by SMOGGED cars and big business under the "Pollution Credits" system. Consider electric cars, Most US power is COAL fueled , Electric cars may not expel smoke , BUT they increase pollution exponentially as they are charged by pollution producing power plants, And most tree huggers don't have a clue . Iam not a "rolling Coal" type , but do believe that no matter how much some one is offended, if I am legal , I don't want to hear it. figure out why its so black, but if its legal and you really need to drive it, Drive on Color of the smoke in no way determines particulate level or pollution rate , Its just black and noticeable, Consider a smog pump, still a mainstay of most car emmissions systems. It does nothing to decrease pollution , it simply pumps large volumes of FRESH air into the exhaust stream "DILUTEING " the exhaust gases to acceptable levels for emmissions, A well built 1968 chevy 350 with just an exhaust pipe can run cleaner and more efficient than a smogged 2000 model , Just sayin.