if your issue is persisting then you may have a vacuum issue in your gas tank. it is not allowing gas to flow into your carb properly.

take the gas cap off or loosen it completely with it just locked in place so gas does not splash out and run it down the highway. that is the problem i was having. i thought that it was my valves needing adjustment but it was not. the bike did like the valve adjustment but it gradually did start sputtering at speed on the highway again.

2 trips to the dealer has now officially fixed the problem!!! i also went down on my jetting since i went way too big (135). when the mechanic fixed the jetting it made the problem worse!!! then he determined it was a vacume problem. i went down the highway with the cap loosened but locked in place and it was much better. they replaced a vacuum line and boom. fixed.

if your problem is resolved after all, that is fantastic!!! i just wanted to mention this as we had the same symptoms but i knew it was not my plug as it has been replace a few times already.