in game settingsIncrease saturation.
Decrease linearity.
Reduce the overall rotation of the wheel.
Tell us how you have it setup now and we can give you better advice on what to change.
Yes as Michael says, suggest reloading the default controller, then set any custom key mappings you need, Then change 'controller overide' to wheel.
Give that a try on track, if its still too slow for you, go back to the options and increase the saturation gradually and test it out until the steering its more responsive.