The GP Wiz (anything that shows up as a game controller) is the issue. Unplug it while mapping the controls that are on the wheel. If you want to also map some buttons from the GP wiz, it has to be done while the wheel is unplugged. (Plug in only wheel, map controls on wheel, exit emulator, unplug wheel, plug in gpwiz, launch emulator, map gpwiz, exit emulator, plug both back in, launch emulator and they should both work in game)
At least that's how it worked for me. That's a pretty old wheel there IIRC. Some of those early wheels don't play nice because there was no standard protocols for force feedback yet.