I'm an armature modeller guys. I threw meticulously pieced together this sonnovabitch in four hours. Its still in development. I plan on the speed to vary, depending on your boost gauge. How would I add a script where it has a bar like the fuel jet player but instead of jetting your car goes faster and eats up the bar, then recharges when you drive normally?
I don't think there should be a boost gauge.
That isn't Mario kart-ish. And from what I can see, you're attempting that style of play.
You should have a selection of different types of carts. All/Some with the same model that preform differently.
For instance, a "Bowser" type kart could have lower speed, but a better turning angle and weight.
Things that keep the kart relatively equal to others, but different in their own way.
Karts of the same class
Class: AI have come up with a quick kart advantage/disadvantage writeup.
Percentages are based on the most effective settings and lowered or increased depending on the kart's status.
150% Percent weighted per kart.
-Bowser Kart
65% Normal speed
85% Turning angle
-Mario Kart
90% Normal speed
60% Turning angle
-Luigi Kart
75% Normal speed
75% Turning angle
-Peach Kart
80% Normal speed
70% Turning angle
Also, I would be more than happy to help with anything you need.
I won't do the models for you, because this is your project. But, if you need help exporting/bringing into game. Let me know.