1) If you're only looking for more umph for daily driving, then the JRSC will suit your LS fine. However, for those wanting high horsepower from their LS, the JRSC will not fit the bill.

2) You will need an intake, and if you want, you can upgrade your header and exhaust. If you keep the exhaust side stock, you will only be choking your JRSC to death. A 2.36-2.5" exhaust diameter is perfect, so you can get a more practical exhaust to keep quiet (APEX'i WS II).