I've had a few of those and they can shift some volume.
The impeller won't push air, so you do have to bleed the air out of the hoses and top of the filter housing. To ensure it doesn't suck air in its best to have it on the ground, rather than sitting up high and open the valve in the lid until all the air vents out. When you bleed it, turn the power off so the turbulence in the filter doesn't draw air in as well.
Make sure there isn't some crap in the housing interfering with the impeller too.