You'll see gains similar to a chambered aftermarket exhaust like the Apex'i World Sport.
If everything's in good shape, I'd go for it.
There were minor changes in the length of the exhaust manifold and catalytic converter...so you may need to have a muffler shop fabricate an extension if your manifold and cat are shorter than the type R setup.
I'm assuming that your LS is a 2dr coupe. If it's a sedan, some tweaks will need to be made...
