Removed the rear muffler from my 323is around 100k miles to upgrade to an entire OEM m3 exhaust system. The stock muffler features the exhaust flap and is in good condition. It would be a good replacement compared to spending over $500 for an aftermarket muffler. Asking $120
Part number 1 in the diagram:
http://realoem.com/bmw/showparts.do?mod ... g=18&fg=20