Valve Seat Correction Angles
WARNING: This page is about a different car, the 2002 Lexus LS 430. However, it is still accessible from the selected car via links, so may be relevant.
If valve seat is too high, use 30 degree and 45 degree stones to lower valve seat contact area. If valve seat is too low, use 60 degree and 45 degree stones to raise valve seat contact area.