Abstract: A muffler including an internal assembly formed of a pair of identical stampings. The internal assembly includes three tubes extending longitudinally between baffles. The internal assembly received within the muffler outer shell forms central upper and lower attenuation chambers as well as chambers at each proximal end of the muffler. The stampings are provided with impressions for forming weep holes and allowing acidic condensation to exit the central chambers. The stampings are located in mirror image relation with one another and are attached to one another by a rivet pattern and using the metal of the stampings. The rivets readily allow acidic condensate to flow between the upper and lower central chambers. Louver-shaped openings are provided on the stampings providing communication between the formed tubes and the upper and lower central chambers and thereby providing attenuation.