For 400hp Budget around 6K+ for Engine and turbo conversion and then you can start on getting the power to the ground, Lsd, semi slicks, traction/launch control, strenghened gear box if your on 5 speed, Clutch and flywheel, suspension etc, decent brakes if you have not all ready got them.
You really need to speak to who ever is going to map the the car for fuel requirements.
Turbo's your looking at something like Owens IHI/Garret or Garret Gt3071R more choice of manifolds for the Garret, Both will be fairly laggy though.
Oh and last but not least a endless pit of money