You really need to tweak the setup for mouse/keyboard driving.
- Lower the steering lock. In the Control Panel, set a low mouse motion speed.
- Experiment with the setting for parallel steer. A high setting makes the car twitchy, in my experience.
- Set the diff-lock setting low. Start at 3 or so, then take it higher if you can handle it. WR sets have it at the maximum (20), but that makes it hard to accelerate out of turns without spinning.