Borla S-type cat-back exhaust systems feature patented straight-through and multi-core technology to unleash hidden horsepower in your 2005 through 2009 Mustang 4.6L and 5.4L, and produce a more aggressive sound and higher flow. Increased exhaust velocity adds power, driving excitement, fuel economy, and the distinctive Borla Sound of Power respected by motoring enthusiasts everywhere. Each Mustang exhaust system is built from premium 300-Series austenitic stainless steel, superior to T-400 Series knockoffs (such as 409), to give you the absolute best in performance and durability. Ultra-smooth mandrel bends ensure maximum flow and power, and precision computer-controlled CNC manufacturing ensures an accurate fit. Best of all, Borla stands behind every 2005-09 Mustang exhaust system with a Million-Mile Warranty. It's just what you'd expect from the world's most experienced (and most winning) exhaust brand.