Kooks Custom Headers for LS1 powered 2004 Pontiac GTO are made from high quality 304 stainless steel. Kooks headers are made to exacting tolerances for high performance improvements and excellent fit. Headers include O2 extensions. Also available is a 3 inch converter connection pipe with high flow metallic catalytic converters part number 6700-CC. Not legal for sale in CA or on emission controlled vehicles. KOOKS racing exhaust products are built for off-highway use only.