Using the standard bars on my 600 Fazer and found that I was getting problems from vibration through the throttle grip, particularly on longer stretches of constant speed running where 50mph average speed cameras are operating, etc. Left hand grip was fine.
I was considering, carb balancing, foam grips, heavier bar ends, etc. etc. but after a bit of investigation I realised that the throttle tube seemed to have excessive clearance over the inner bar in that you could rattle the throttle at standstill. I whipped off the throttle tube and after cleaning the bar I applied 3 short lengths of electrician's tape running outwards to the end of the bar and spaced equally around the circumference. The throttle tube still cleared and operated fine but without the rattle. I sprayed it with GT85 and reassembled.
Just had a test run for an hour or so and the vibration has disappeared. Result!