As has been said the st170 is not an easy car to improve power wise without high expenditure.

The main advantage that it does have is that it handles well. A few choice mods to the handling can really improve the performance of the car and what you can get out of it I have eibach springs, dampers and arbs on mine and whilst it may not be the most powerful car out their it can out handle many cars with higher power.

I have done a few mods to the car in terms of induction and exhaust but these do not produce any noticeable gains.

Best mod I did to mine was acquiring a dreamscience stratagem handset and remapping it on the most powerful map available.

As has been said before they do not sell them new anymore for the st170 but they do come up 2nd hand or you can get the maps put on at authorised dealers.

This has been the most worthwhile mod on my car power wise as you can feel the extra power. The other main advantage is that the st170 tends to suffer from flatspots in the power curve the remap has cured this and means that it will accelerate a lot harder.

al