I would love more specific tuning and racing catagories. You don't just go out and buy a racing exhaust, you look at your options - Titanium, stainless steel, etc. More precise aero tuning, like underbody panels, diffusers, vents, fender flares, splitters, canards... buying a rear wing doesn't let you do all of that! And with that stricter racing catagories, similar to SCCA autocross. some tracks have decibel limits, and you would have to choose your exhaust system based on that for example. And more advanced options like choosing boost pressures. What about techno wonders such as anti-lag, variable geometry turbos, active differentials. Lastly, better ways to understand the cars as you build and tune them. things like a dyno (and a better marked dyno graph for that matter), wind tunnel, tire pyrometer, and such.