TestDrive Unlimited supports TrackIR (pitch and yaw only though, no roll). I made a program for emulating TrackIR with the VR920. You can download my program here:
http://rapidshare.com/files/55592903/GlovePIE-VR920TrackIR.zip

Extract it to a folder, then run the GlovePIE.exe. Make sure TestDrive Unlimited is not currently running. You should then open the FakeTrackIR script in the VR920Scripts folder. Then press the Run button to run the script.

Now you can start TestDrive Unlimited. While the FakeTrackIR script is running, the game will see the VR920 as though it was a TrackIR.

Here are the instructions for how to enable TrackIR support in the game.

http://www.naturalpoint.com/trackir/03-enhanced-games/game-test-drive-unlimited.html

You will now be able to stop the script and start it whenever you want. It is only the very first time you run it that you have to run it before you start the game. Now whenever the script (or GlovePIE) is not running the game will still think you have a TrackIR, but it will always be zero, or whatever you last set it to. Starting the script will make it report the VR920's values again. If you have a real trackir you can restore the real trackir from the CP-Settings menu.

Let me know if it works or not. My VR920 hasn't arrived yet, and I don't have TestDrive Unlimited.