The main difference between Magnaflow and Flowmaster exhaust kits is their method of noise reduction. Magnaflow mufflers are packed with steel wool, which lasts longer than fiberglass packing often used in lesser mufflers. Flowmaster mufflers contain no packing at all, and noise is reduced by a series of engineered baffles.
Most Magnaflow exhaust kits are made from stainless steel and feature polished mufflers for a clean under car appearance. Flowmaster kits incorporate aluminized steel with stainless steel, and the mufflers are not polished. Kits from both manufacturers are made in the United States and represent a significant upgrade over a vehicle's factory-fitted exhaust system.