one would think that a metro car being 1000cc displacement which is almost 3 times a much as a banshee, the turbo would be plenty big.
i know from dicking with my turbo buick you cant slam a big turbo in for the power unless you have a 3000 + stall convetor cause of the lag.
i would run a some what smaller turbo that boosts fast, and more boost to it, but dont get to carried away with boost. 7 psi is 50% more power.
i like the idea of a computer setup up, really smart way of doing it. how are you going to do a fuel pump and what is your fuel pressures going to be at.
i would port it, so its more effecient, it will me mostly mid to top and ways i would just drag port it with a good exhaust dur. to get the gases out.
best of luck
im sure it will fly