I made a Touge tune for the Rx8. It’s on street tires so don’t expect it to drive like a race car.
I tuned it as a street to track car. You can tweak the car to your preference and try sport/race tires if you want
I also made a simple Formula to get a basic calculation for your spring rate.
ENJOY. FORZA HORIZON 3 Touge | Street Spec RX8 | Tuning Guide - YouTube