If it's never been done, check throttle body sync. If that's good, and all fasteners are correctly torqued (engine mounts, upper and lower triple clamps, handlebar clamps), I would replace the grips. Seriously, I've used
Pro Grip 714's on every bike I've owned since 1994 and there have been a lot of them. Singles, parallel twins, v twins, triples, inline 4's and v4's.
They are slightly larger in diameter and super comfortable...and they reduce vibration (singles and twins) or buzz (inline 4's) noticeably. The grooves you see are for optional safety wire.
If this doesn't satisfy you, next step would probably be the 2014 upgraded clutch basket.