All pipes carrying exhaust gases from the motor shall be constructed of, and maintained with, leak-proof metal. Exhaust pipes shall be directed from the muffler or mufflers toward the rear of the vehicle and shall be approximately parallel with the longitudinal axis of the vehicle and approximately parallel to the surface of the roadway,
or shall be directed from the muffler upward to a location above the cab or body of the vehicle so that fumes, gases and smoke are directed away from the occupants of the vehicle. Exhaust pipes on a passenger vehicle shall extend to the
extreme rear end of the vehicle's body, not including the bumper and its attachments to the body, or shall be attached to the vehicle in such a way that the exhaust pipes direct the exhaust gases to either side of the vehicle ensuring that
fresh ambient air is located under the vehicle at all times. The Commissioner of Motor Vehicles may adopt regulations in accordance with the provisions of chapter 54 to establish safety standards for passenger vehicles equipped with exhaust pipes located in front of the rear axle.
At least I know stacks are legal. So IF I ever DO get a diesel
But, as for what's in red, I guess it's illegal. I do see some trucks around with dumped exhausts though..