How do you use the boost? in the n64 version i played back in the day, you used use point the analog stick up to build the meter and then hit a button to use the boost but i can't find anywhere in the menu controls on how to do that. I've binded the key to the actual boost command but what i mean is where's the 'build up' meter command?

Go to the controls and assign something to nose up/down.

initailly i assigned it to the up/down axis on the left stick of the 360 pad...
Don't do that, as then it's very hard to charge boost and also steer.

Set it to up/down on the right stick.

Then to activate it, hold up when at full speed, when the dot changes colour hit the boost button.

When the heat warning beeps get frantic, just release the throttle for an instant to cancel the boost (or the engines overheat)

Did you manage to get it recognize the Y-axis 'the right way'? Mine is always up = up, down = down, not the other way around as it should be, regardless of whether I set it to inverted or not.