Electric fuel pump issues

I just replaced the electric fuel pump on my 71 Duster 360/380 crate engine with a new Holley blue pump and regulator. It has a new 3/8 fuel line on it. The problem that I am having is that when the engine is cold I have the fuel pressure set at near 8 psi. After the engine warms up it drops to 3 psi. Sometimes the regulator doesn’t react very well when attempting to adjust. Has anyone else had any trouble with the Holley blue regulators? The fuel pump is mounted on the passenger frame rail slightly higher than the pick up tube coming out of the tank but I never had any trouble with this configuration when I was running an LA 360 in this car with a different Holley blue pump and regulator. Any ideas?