If you're looking for an exhaust manifold that will improve your performance and throttle response, the AFE 46-40012 Ductile Iron Exhaust Manifold is the perfect choice. This manifold is made from thick wall (0.25" vs. 0.15") T3 flange material, which provides superior durability and improved throttle response. Additionally, two Exhaust Gas Temperature (EGT) probe ports are supplied, allowing you to monitor your engine's performance. The AFE 46-40012 Ductile Iron Exhaust Manifold has been proven to outflow the factory exhaust manifold by up to 23%, making it the perfect upgrade for your 2003-2007 5.9 Cummins engine.