The system operates fine at the maximum pressure the air comp puts out. I did notice that the regulator mounted to frame is very small. Regulators and solenoid valves used in comp air systems have a "CV" value. CV value refers to flow. The greater the size of valve and ports-the greater the flow. Judging by the air cylinder size and the size of the pressure regulator, I would say there is a flow problem through the regulator. Running without the regulator will help to increase flow to air cylinder.
I have two A3 trucks-one steers easy, the other is a little harder. I do notice the easier steering truck affects the air pressure guage in the truck much more-when turning, the pressure goes down quicker. While on the harder steer truck, the pressure guage is more lazy when turning. Indicates issue with regulator and flow. If air cant get to cylinder, the compressed air reading wont be affected as much.
My two cents worth.
Pete