if your looking for that sort of power i would suggest getting a HKS turbo, injectors, fuel pump and PFC d jetro that should get you very close to 300 rwkws without having to start spending to much money on engine internals...
mate of mine just put a HKS 25/35 on his R33 and made 245 rwkws with 14 degrees of timing and 14 Psi of boost and the only other mods he has is straight through 3 inch exhaust and pod filter.
This was all done by Tilbrook Auto.. they did a great job.