[p3lim]

Try adding this:

TextStatus_UpdateString = function() end

or if that doesnt suite the needs (as it disables text for healthbars too), try this:

PlayerFrameManaBar:UnregisterEvent('CVAR_UPDATE')
TargetFrameManaBar:UnregisterEvent('CVAR_UPDATE')
FocusFrameManaBar:UnregisterEvent('CVAR_UPDATE')

With the second one you might need to add the following, but I havent tested it.

PlayerFrameManaBar.TextString:Show()
TargetFrameManaBar.TextString:Show()
FocusFrameManaBar.TextString:Show()