isx 15 400hp vibration

[Hotshot]

Hey Y'all, brand new to the forum wondering if i can find some more info on the possibility of my crank dampener being the cause of my high rpm engine vibration under load.
All driveline and clutch potentials have been eliminated as the cause. Vibration is strictly engine rpm related and can be brought on or off with the throttle pedal from 1550 on up to the top. engine has 611k on it. any help will be greatly appreciated. Thanks