250hp with minimal lag is the hard bit mate. We know the power is possible but even these days it isn't easy.
A good efi manifold is what you need. Maybe michael T can help you with that.
A good exhaust manifold too.
Probably stick with the bp285 cam, it works well enough. The later (or was it earlier ?)112 LSA if you can find one.
Phil's VNT powered EFI conversion shocked me, it worked better than I thought it would (never having done anything with a VNT before). The VNT made over 260hp at about 27psi, I hope he doesn't mind me saying that. That was minimal lag with boost controlled by the ECU so we could dictate the shape of the torque curve and avoid boost spikes.
One large intercooler is all you need.
Saab "red" 2.3L turbo injectors are common, they'll do you.
BKR8EIX for the plugs