I tested ride height, backwards effects, spring rates, backwards effects (it would seem) and anti-roll bars, backwards effects. This being on a FWD car. Rear toe was correct, as was brake balance. I assume LSD is correct but it has very little effect if any at all on one wheel spinners in this game. Front toe has always been backwards, but I forgave that (negative front toe value has effect of toe-in). I know I struck a nice balance with many of my cars, from an understanding of how the game worked, but now I see that some of my cars could be better with real tuning effects.
Thanks praiano, I wish I could play both as well. Unless money flow changes I'll be sticking with GT5 though, it's not like I have much choice.