Good morning Simon,
In answer to your question of me about achievable results with your car, it is my experience that you will not see an honest figure in excess of 275 bhp or so with your car. This alone is a very significant gain over your basic figure.
The problem lies with the very small earlier Mitsubishi TDO 4 familly turbos which will not sustain high boost pressures at higher revs.
You can remedy this in part by fitting a larger turbo from a later model, but you can then be close to the limit with your weaker rods that were upgraded with the 850R and subsequant S/V/C vehicles. Special downpipes with very efficient cats and free flow exhausts from there back will also help, but with these additional items you will still not see a great deal more on the very earliest cars, again with the caveat that they should be in tip top order.
Separate from my own experiences are the results shown at third party rolling road sessions organised by this and other clubs where results from Superchip, TME, Rica and Dastec/Unichip systems have all been within just a few bhp of one another.
Don.Norchi.
www.kalmar-union.com
TME engineered software UK distributor.