Varistream 2 with 100mtrs 8mm microbore and I use mine at 10 'O'clock for normal use or 11/12 'O'clock for a first clean.
What I found was I spent about an hour playing with the blue pot in the varistream and my hose pulled out a different lenghts until I had the optimum setting on my varistream,
I now have an excellent jet from my brush head, play around with your varistream pot until it gives you your desired flow rate.
There are no 2 set-ups the same, even though we have the same equipment from the same manufacturers, small variations in the Tolerance's of electronic components see to this, the only way manufactures of electronics can give a near true indication of tolerance, is by using top quality components of 1% tolerance, and not the 10% tolerance I have in mine. this would then add about another 30% to the price of a varistream.
Your battery capacity also plays a part, this can also be governed by the cable size and lenght and battery clips we use.
Also the hose's may be from different batches, this may create a slight difference in hose diameter and the way its wound on the reel can play a small part in different flow rates.
So you see, no two systems are identical and we can only give you a guid.
The only true answer, is to play with your own varistream, until optimum pressure at your brush is obtained.