Engine will take 400bhp, maybe a little more. Getting that far on the standard injectors may be a struggle and to go for bigger injectors would really necessitate a management change, which might be a struggle on your budget.

Also, if it's on a standard Clutch, £1500 of that budget is already spoken for on a proper Clutch.

I think I'd fit an Evo 9 Turbo, Tubular Manifold, Cams, Boost Controller, Ecutek Remap and a Twin Plate Clutch.

That'd be about it for your £4k!!