That's the only Logitech wheel for Xbox 360 I guess, it's basically the same as the Formula Force EX on PC.
I don't know the options in Forza 4, but you should either try lowering sensivity/linearity or use speed sensitive steering. It should also depend on what steering lock the cars have. If it's something like 13-15 you should use around 25% sensivity, if it's 20-30 then go for 10-15%.
Speed sensitive steering is a bit more complicated, but you can experiment with that. In the first case of steering locks around 50% can be a good value for that.
Try searching for these settings in the game's options menu. If you have both options, try each and choose whatever you like better.