DNA Motoring HDBIS300 Stainless Steel Exhaust Header Manifold [For 01-05 IS300] Made of High Quality T304 Stainless Steel Material Covered with Ceramic Coated TIG Welded CNC Machine Flange 2 x 3-1 High Performance JDM Racing Spec. Design Increase High Flow Air, Instantly Gain 10 to 15 Hp./Tq. Inlet/Outlet: 2.25" / 2.25"; O2 Sensor Bung Insertion and Metal Gasket Included