Spec-v Stainless Steel Header Exhaust Manifold For 2002-2006 Sentra 2.5 Ser Material: T304 Stainless Steel 4-1 Racing Spec. Design O2 sensor & EGR bung insertion; Metal gasket included Increase high flow air, instantly gain 10 to 15 horsepower or torque Utilizes Factory O2 Sensor Position, O2 Sensor bung is welded on tubing so stock O2 sensor can be plugged in