I put bluefin on mine, and although I could feel the difference it wasn't that much. The ST170 is already fairly well tuned and I think a car generally needs a turbo (Diesel or petrol) for chips to make any major improvement.
What I noticed from bluefin
- car picks up quicker
- slightly smoother
- the extra power/torque in 5th and 6th when cruising

Just my opinion