Hi,

I have a Phantom 2 with a Zenmuse H3-3D gimbal for my GoPro Hero 4 Black and an iOSD mini FPV kit and when I go full speed I notice there is what looks like vibration on the gimbal in the footage. Here's an example: https://vimeo.com/176844114

Is there anything I can add on or calibrate to fix it?

Thanks

First thing to check are the 4 rubber dampers on the gimbal, make sure they are not torn and that the 2 anti drop pins are fitted properly. They need to be able to move freely,  not cable-tied tight to the mounting as I have seen some fitted.
Next would be the props as out of balance or damaged props will cause a lot of vibration.

In addition, it would be better to perform an IMU calibration.