I installed a factory dual exhaust system from a Ford Interceptor on a 2009 Mercury Marquis, they all come with a single exhaust. I wanted a good sounding muffler but not some crappy freeway rumble, I'm not 16 anymore. Those Magnaflows, which are basically very tightly packed glass bags, sounded great. No hum and very good sound outside the car. A friend drove the car and polished it and I stood in the driveway listening to that amazing noise. The last time I made her do this she almost yanked the rear wheels off my supercharged Ford Harley truck when she forgot to let off the gas, GOSH!