@kowenicki
It's true that I installed it, but many simple modifications can be done to your nowadays car that most people don't know about it.
I also disagree with Skeeuk with Forza being more arcade than sims when it comes to tuning up the assists to different degrees. Forza 3 handles pretty well the driving physics with all the assists off, but the one thing that I really think that's outstanding in the game it's the opponent's A.I.
In advanced they use every trick in the book to overtake you, throw you off the track, they use the slipstream cone like true pros, and they seem to always get the best Torque RPM curve like most professional drivers do. I saw the telemetry of a RS8 opponent, and he managed to handle all the shifts at the maximum Torque peak of 4400 RPM of the RS8, that just blew me away.
Current PC Build
CPU - i7 8700K 3.7 GHz (4.7 GHz turbo) 6 cores OC'd to 5.2 GHz with Watercooling (Hydro Series H110i) | MB - Gigabyte Z370 HD3P ATX | Gigabyte GTX 1080ti Gaming OC BLACK 11G (1657 MHz Boost Core / 11010 MHz Memory) | RAM - Corsair DIMM 32GB DDR4, 2400 MHz | PSU - Corsair CX650M (80+ Bronze) 650W | Audio - Asus Essence STX II 7.1 | Monitor - Samsung U28E590D 4K UHD, Freesync, 1 ms, 60 Hz, 28"