I just ordered those today myself. I have been trying to get rid of the vibration/rough running and this is next on my list. Just to recap here is what I have done-

Rebuilt carbs, new needles with Viton tip, new floats, etc.
Rebuilt gearbox.
Synced many, many, many, many times. Bought the throttle adjuster from Highwing LLC that has been helpful.
Changed plugs

Anything I have forgotten? Thing runs glass smooth from 2500 up- pulls 5200 on climbout, just rough running at 2500 down. Very annoying on base to final