Yup, a black plug is a definite sign of carb issues.
I'm not a big fan of either the BR8ES or the BR8EG (nickel). While both are fine standard duty plugs, you are riding a high performance machine. Platinum has a higher melting point, and thus longer wear. Iridium plugs have been all the rage, so I tried a couple. Didn't like the performance as well as platinum.
With a properly jetted and tuned bike, you should notice a performance improvement when switching to a BR8EVX. I know that Team Green recommends the BR9EVX to get the proper flame front, but I've just never taken the time to rejet my bike for a BR9EVX. Just too lazy...
Rick