Factory Nismo Exhaust????

You don't just magically get HP from adding different exhaust pieces together. It's all about the flow of air inside the exhaust. The more flow, the more the engine can breath and the more HP which can be "made." So the less bends, the less restrictions, and the wider the pipes the more power, but also more noise. Catalytic converters restrict the flow, as well as un-mandrel bent pipes. Also, the exhaust can only flow through its most restrictive point. So if the ENTIRE exhaust was 3 inches, but one small section of pipe was 2.5, then the whole exhaust would be limited to that one small 2.5 inch flow. So if your whole exhaust system is 2.5 inch (idk what the 350z diameter is sorry), and you add 3 inch mufflers, it won't do a ****, it will just most likely be louder.

BTW, yes it does. My best friend has it on his 350Z. It is a complete system, with larger Y-pipe, in his case.

No cats!!!!!!!

Well I already took off the factory cats..and replaced with race stright pipes..plus added a y pipe....the only part not changed is the rear muffler, that why I asked if I put on this factory nismo muffler would it be a hp gain, also I have stillen long pipe and duel Intakes. ??? ???