run xvidtune from an xterm
correct your screen, to work at a higher refresh rate
click "show"
you will get a line of numbers pasted to your xterm. close it and now copy that line into XF86Config-4
Code:
Section "Monitor"
...
VertRefresh...
ModeLine "1024x768" 94.50 1024 1036 1132 1260 768 769 772 796 +HSync +VS
ync
#or whatever you got. if you havent figured it out yet, the 94.50 is the refresh rate.
cheers.