Yeah, you need twin scroll headers and up pipe, which also means you'll need a new sump and oil pickup. Vision R sell tomei twin scroll headers, and psr over east sell gt spec ones. I had GT Spec ones on my conversion, just make sure you get the gaskets, as they are hard to find. For the price JWS charge for subaru ones, your better off going down the aftermarket route, unless you want to buy that VF36 kit which is on sale on rexnet at the moment. Its quite a good price. The VF36/37 is capable of supplying a lot of boost, but you need to modify the wastegate (i.e. make it stronger) to keep boost up top. Trust me, you won't regret it.

__________________
John Stamos fan club lifetime member