dude most of the residue is cus oil is leakin on hot engibne parts mainly the exhaust thats why its kinda smokin. might be a sludge buildup or some sore to cause the leaking. how often have you gotten a oil change? just make sure the thing isnt seeping cus if it is you got a prob man. idk sounds like you might have to replace your gaskets i would so to stay on the safe side.