If you go to Toyota's media site, you can see this graphic which shows the change they are making in their pedal.
The toothy thing is a pedal feedback mechanism which uses friction to give the pedal a certain amount of resistance at the end of its travel.
What Toyota is doing is putting a shim in behind the pedal arm, to limit its travel. Which means that unless they reprogram their ECU to interpret the new position as WOT (wide open throttle), customers won't ever be able to get to WOT--instead they'll top out at 97% or whatever the new maximum travel point corresponds to.
So in addition to installing "precision cut steel", I would expect Toyota to also have to spend a few minutes on each car to reprogram the throttle pedal calibration curves. Unless, of course, the extra few percent of travel isn't needed.