I use vi, others use emacs and other others use something else. vi
might be complicated at first, so you might consider another one (I'm not familiar with them).
Do you still have your original X configuration file? It's easiest to use that one (I think).
You most probably have to modify the lines HorizSync
in this file. Look in your monitor documentation to find the values for these settings.
You might be able to find these values using your monitors OSD, but this is a bit more work.
A very short emacs help in this thread