[ossiblue]

Tirwin has a good point as many times the mixture screw is adjusted to compensate for wur issues. I would suggest you take a step back and set your wur to spec for both warm and cold pressures. Since your warm pressure is low, you can do the adjustment without removing or disassembling the wur. If you choose to do this, read the following:

Set your warm pressure first. With fuel gauge hooked up, plug in the heating element, jump the fuel pump relay, and turn on the ignition to the "run" position. Monitor the control pressure until the top of wur feels hot and the pressure has risen to its highest reading. Using a socket extension (or something similar) and a small hammer, slowly and carefully tap on the top of the wur in the area between the fuel inlet/outlet. What you are doing is moving the cylinder that holds the pressure diagram, downward onto the pin that controls the pressure. Watch your gauge, work slowly and continue to tap the cylinder down until your gauge reads the correct warm control pressure for your wur.

Once the warm pressure is set, wait until the wur has cooled to ambient temp. Now, unplug the heating element and check the cold pressure. If it has changed, it will be higher than before and you can easily lower it by tapping down the plug for the bimetallic arm.

By putting your wur into spec, you've eliminated it as a problem. It would be a good time to check your A/F ratio as tirwin suggested.