Setting the force feedback seems to do nothing to the G25's, It seems as if its set to a fixed point.
You might try playing with the power steering setting. Or is that active steering? Sorry I forget.
I'm not at my PS3 so can't check it but a button combo changes it from 900° to 270° steering, something like holding SELECT+R2+R3 as you start the game.
Can anyone confirm this?
I've heard you can do this on the DFGT, how about the G25?