Moninfo is good stuff. I had a ViewSonic TV that advertised its native resolution over the VGA port, but over HDMI its default res was 1280x720, while 1280x720 was also in the VESA mode list.
So I captured the EDID from the VGA and HDMI, then I modified the HDMI discrete timing info for the default mode to match that of the VGA, leaving the 1280x720 only in the mode list. Since ViewSonic often leaves the EDID writable, I was able to re-flash the modified info into the TV. Hooked up my HTPC and got dot-by-dot over the DVI to HDMI cable.
