Not much in either regard provided the muffler isn't too restrictive. At least around here, the deer don't seem to care that much about a few decibels this way or that from truck exhaust. Case in point, my Dad's '99 dodge cummins dee-smell. That shaking, rattling bastard makes enough noise to loosen fillings and wake the dead. We still see as many deer from the road as we would rolling in a lectric fart kart, which ain't very damn many. That's why we eventually have to shut the rattle trap down and get in the brush when conditions are favorable for foot stalking.