I may be going off topic a little here but on my first 660z I noticed vibrations increased when I fitted the Yamaha engine bars. It's possible vibrations worsen when various types of engine/crash bars are fitted and the engine vibes are transmitted via the bars to the frame/seat/footpegs/handlebars.

Not sure how having a full or empty fuel tank will change the amount of vibes though.

(the original Yamaha brs cracked,, changed themunder warranty and the second set cracked)