Seen side-by-side, we can see where the MagnaFlow system (PN 15706) adds a bit of diameter (2.25-inch vs. 2-inch) and smoothes out the bends. The factory muffler is both quiet and restrictive, where the MagnaFlow part is a high-flow, straight-through design, and the pipes have gentler bends. It all adds up. All MagnaFlow catalyst-back exhaust systems are stainless steel, too. We'll never worry about corrosion. Careful design and top-quality manufacturing methods and materials make for exhaust systems that should out-last the vehicles they're installed under, and that kind of insurance helps justify the investment.