I'm not sure on this, but I do some programming and think I know why this may
happen in some games. When using a keyboard, it's easy to automatically reach
full throttle (just hit the key!). When using a pedal/joystick setup for
throttle control, it needs to be calibrated. The problem is, when you floor
the pedal/push the stick all the way forward during calibration, the program
may not get the setting correct (to put it simply).
You may want to try calibrating the pedal/joystick a little differently in
the throttle axis. When it says "accelerate all the way (or whatever)" to
calibrate the stick/pedal, push it forward ALMOST all the way, then click or
end the calibration test.
When you now floor the gas pedal/push the stick all the way forward, you
should get full throttle. It's not necessarily going to work in every game,
but from a programmer's point of view, it's a possibility.
Have fun!
Todd
http://PerformanceSimulations.com