John,
I don't think there is a "EXT BAUD RATE" setting. Which menu item are you referring to?
If you are referring to menu 919, "EXT DATA SPEED", this setting is what determines which connections on the 6-pin DIN you will be using. For the highest speeds with Vara FM, set this menu item to "9600", then use a cable that is wired for "9600", and in the Vara FM settings, select Wide mode. If you then connect to another station that is set up for Wide mode, you will achieve the highest speeds (about twice the speed as Narrow mode).
-Scott, NS7C
Scott Currie