I was looking for your HydraBoost or a vacuum power assist can but didn't see them (at least not in the "right" place). Then I realized you where from a place that states keep left on all of your road signs.
There is no vacuum at all in a HydroBoost only hydraulic pressure (over a thousand psi on the high side if you are restricted like you claim (normal is around 750 psi high about 120 on the low side). Your pump may be out putting enough pressure but not enough volume. Aftermarket makes bigger pumps to handle 4x4 rock crawlers.