It depends if you want cats or not. Having both headers and the JoeZ exhaust eliminate both the stock primary and secondaryCats. Both PPE and Sikky come with electronic O2 simulators that you install in lieu of the catalytic converters that fools the ECU so that you don't have a CEL. I have PPE headers with a custom dual exhaust system that utilizes the stock mufflers. I am also running hi flow cats installed into my dual system. If you wanted the JoeZ and wanted cats, you would need to add them as I have done. I am attaching a couple of pics showing my cat installation.I'm still confused about if I got headers and the Joe-Z exhaust if I'd have any cats or not.... Anybody have some comments/useful info about this?