I just got g25 and i also have issues with the pedals on lfs s2(32bit vista). Lfs doesnt recognise the pedals correctly. The clutch pedal is identified just fine but lfs thinks that throttle and break pedals are on the same axis.
If i dont press any pedals, then the throttle/break axis is on the center. If i press the throttle, the axis goes to zero and if i press the break, the axis goes full.
Gtr2 also recognizes the throttle/break as 1 axis but at least on gtr2 you can assign the negative part of the axis to throttle and the positive part of the axis to break. The only disadvantage that you have is that you cant actually push the throttle while breaking cause throttle negates the breaking axis but at least it works.