Hi Kazem,
I've found the unit becomes virtually worthless by removing the portion of the nozzle that is beyond the blade.
The best you can get is around 70% pick up focusing on the finer dust by forcing the air directly through the gullets of the blade to move the fine dust. By opening up a larger area to draw from you're switching from using velocity to collect the dust into trying to use volume or mass air flow to collect it, which this nozzle doesn't handle period.
It'll never get the larger shavings and chips, as shown and discussed in the videos. However, closing up the overall saw guard exit points does notably improve the pick-up percentage as it contains the shavings closer to the nozzle.
I'll go ahead and send another nozzle over.
Thank you!
Jacob