Slid the engine cover off 1997 dolphin, 460 gas engine to troubleshoot some air conditioning, defrost, ducting problems. Noted the underside of the engine hatch cover had black soot along both side in sufficient amounts such that some dropped onto the floor of the coach as we wrestled with the cover. BUT--couldn't find any soot on the engine, hoses on top of the engine or any of the parts on the top or side of the engine. Suggests to me an exhaust manifold leak but all along both sides about 4 inches up from the bottom of the side pieces??? BUT didn't hear any exhaust noise that would suggest a leak. How come I don't see some soot on the engine? Maybe the distribution was from the airflow and not multiple leaks?? Help.