A dual-mode exhaust system includes a housing with an input port attached to the existing muffler exhaust system and positioned downstream thereof. The system further includes a mechanism for selectively distributing vehicle exhaust from the input port to the first and second output ports, upper and lower chambers vertically stacked within the housing, and first and second vertically spaced pendulum arms disposed within the upper and lower chambers respectively and anchored at respective distal ends thereof respectively. First and second vehicle exhaust pipes are coupled to the first and second output ports.