Why in the heck would you want to use a PID for controlling a throttle body? I know a fair bit about cars, and bit about PID algos, but I fail to see how a PID helps you. PID are fairly slow algorithms by nature, they are designed for systems where there is lots of lag and overshoot, noise, or ripples. Furthermore, your servo will have a PID algo built into its controller for the purpose of maintaining a set position against any disturbances. Finally, what you want out of a throttle control is speed and a direct, linear relationship to the loud pedal. Don't muck it up more than you absolutely have to.
The reason that carmakers these days use electronic throttle bodies is because it gives them the ability to "get in the way" of the driver for the purpose of fuel economy and safety (traction control). Since you're in FSAE hybrid, the former is probably your concern. What I'd suggest is a "race" map for the Autocross portion - with a 1:1 mapping of throttle pot to throttle body - and an economy map for the efficiency portions of the test - using some damping factor.
You should have a well-trained driver in the cockpit, so don't make the throttle body the brains of the operation.