Custom Resolution Utility (CRU)

[ToastyX]

It's possible you're editing the wrong one. Each connection creates a separate entry, and there may be outdated entries that aren't being used anymore. CRU should pick the first active entry it finds, but if you're not sure which is which, delete all of them and reboot. Then the list should only have entries that are currently active.

With AMD/ATI, sometimes the highest refresh rate has to be listed as the first detailed resolution or the video driver will ignore it. You can also try unchecking "Include extension block" if that's checked.