Brian, 4 will be plenty of pressure for your truck. The regulator springs are colored, but I couldn't tell you what it is, you can tell with both side by side, the higher pressure has bigger wire.
The pump has a by-pass valve in it to keep from burning out the motor when the flow stops, it might be sticking letting the pressure rise and fall. Pull the screw cap off the lower side of the pump (about dime sized) and see if the valve moves easily. Thats about the only thing that will cause it to rise, but the regulator should control it. Try plumbing a gauge right to the pump, it should hold steady when plugged once the relief valve opens.
Next install the regulator and recheck pressure on the outlet side. Going one step at a time is the only way you are going to solve it.
Joe
