DNA Motoring HDS-AI94RS-41 Stainless Steel Exhaust Header Manifold Made of high quality T304 Stainless Steel material; 4-1 design TIG welded CNC machine flange; direct bolt-on installation, requires no modification Increase high flow air, instantly gain 10 -15 HP./ TQ. 1.75" inlet/ 2" outlet/ O2 sensor insertion and metal gasket included Professional installation is highly recommended; installation instruction is not included