I have got a Samuk B25L (made by hangcha HC) the steering works ok when turning steering wheel slow but if you try to turn steering quickly for example if you try to drive in a figure of 8 the steering stiffens as if there is not enough oil flow. The priority valve is built intto the main valve block. You can increase the pressure but it doesn't make any difference. The relief pressure is currently set at 1400 PSI. The steering oritrol is an Eaton BZZ, there is no adjustment on the steer orbitrol.