I tried lowering the idle speed and started to get a harmonic vibration from the hydraulic pump(s). It sounded very similar to your video only more pronounced. I suspect that is one of the reasons for the higher idle speed setting.
You can adjust both low and high idle (full throttle) with set screws on the side of the injector pump. You'll need two 10mm open ended wrenches to adjust them. Your cable might have to be adjusted too. When you take the right engine side cover off, it will be self explanatory. :good2: