My truck did come with a cat, which is layin in the back of my parts truck with my old exhaust now. I just put headers and dual exhaust on my truck, no cats. I also removed the AIR system-those pipes going into the exhaust manifolds. If you have emission testing in your area I suggest you get headers with the AIR system inlets, and put cats on your truck. As for me, emissions testing in CT wont be till the end of the summer, I will probably install high flow cats by then. Oh, and get headers that are coated, or have a high quality paint on them. My Dynomax headers are rusty after 5 months.