For Ford F150 5.4 V8 Stainless Steel Header/Exhaust Tubular Manifold+Mid Pipe Made of High Quality T-304 Stainless Steel with Computerized Mandrel-Bends for Strength and Durability i.e. Maximizing Smoothest High Exhaust Air Flow Rate 2 x 4-1 High Performance Racing Spec. Design, Produces the Most Top End Power Offers the Best Flow Characteristics for the Engine at High Engine Speeds Increase High Flow Air, Instantly Gain 10 -15 Hp. / Tq. Inlet: 1.875"(OD)/ 2.5"(OD) Mid Pipe & Collector / 10mm Thick Header Flange / 16 Gauge Wall Piping / O2 Sensor Bung and Metal Gaskets Included