I noticed as I was taking apart the carbs that a nozzle seems to be broken off the cap of the right-hand carb.  Before I took it apart for a cleaning and a sync, the bike ran half-decent. There were no hoses attached to this hole, thus it can't be critically important.  I can't find any good pics of the top of a GSF carb, nor can I find a part number for this plastic piece.  If anyone could offer some insight, it would be much appreciated 

Take a look at this thread.  It might be answering the same question.
http://gstwins.com/gsboard/index.php?topic=49928.0

Ah, thanks for that

Hello,

There are two nozzles on each plastic cover. One nozzle should be closed and the other connected to a hose form the solenoid valve. This is true for both plastic covers.

If its the open one that is broken, I think it is better to block it (you could also block the left one, or unwire the valve)
The hole assembly (Valve-plastic cover) controls the piston valve lift around 4-6K rpm.