[Mike Pearson]

First thing I would do is to make sure the calipers are perfectly square to the rotor. That is paramount to the brakes working correctly and not dragging. Then make sure the calipers are positioned correctly that the bleed screw is at the highest point of the caliper. After that I would take the pressure gauge and pressure switch out of the system and re bleed and check. Those two items would be suspect to not bleeding completely. You should not need a residual pressure valve.