Need For Speed: Undercover supports force feedback and maps the wheel by default. Pedals, however, will not work on Logitech Driving Force GT Gaming Wheel and will not map. The game doesn't see the wheel or pedals when you try to map manually.
To get the pedals to work and map wheel buttons, download Logitech Profiler (Logitech Gaming Software). Create a new profile and if you got the game from Steam, you can find the executable under C:\Program Files (x86)\Steam\SteamApps\common\Need for Speed Undercover\nfs.exe.
Leave "specific game settings" section alone, "report combined pedals" didn't work for me.
Click on "Accelerator" on bottom left and select Axis Assignment -> New Axis Assignment. Click Edit and record new keystroke "w". Now assign it to Accelerator down and click ok, leaving Accelerator up unassigned.
Do same with "Brake", but instead assign keystroke "s".
Your pedals will now work.
Same way, you can assign other controls to the wheel. Check game controls to see default key assignment, record that keystroke and assign it to wheel buttons.