Fuel pressure climbs at idle

I have a 74 Sport with a mild 408 with a Edelbrock 750 carb. I just installed an electric fuel pump, my first one. I have a Holley blue pump and a Holley regulator. I hooked it up "dead head" no return line. I fired it up and everything works well. I set my pressure right at 6psi. The only problem that Im having is that if it idles for a bit the pressure climbs a little bit. It will go to 10 psi but as soon as you open the throttle it drops right back to 6 psi. Any ideas? Should I even worry about it?