A muffler for coupling to an exhaust port of an internal combustion engine. The muffler includes a housing having an exhaust inlet configured to receive exhaust gas from the engine, at least one internal expansion chamber and an outlet opening. The muffler further includes a diffuser cover attached to the housing over the exhaust opening of the housing forming an exhaust outlet of the muffler. The diffuser cover forms a trap chamber, a restricted throat and an ejector portion. The ejector portion is configured to draw in ambient air through an air inlet to cool the exhaust gas as it passes through the exhaust outlet. The restricted throat is positioned downstream from said trap chamber so as to increase the velocity of the exhaust gas as the exhaust gas passes through the restricted throat and into the ejector portion so as to aid in drawing in ambient air.