Does your fuel pressure regulator work on a vacuum? What I did was use a vacuum regulator, used the old emmisions fuel line (the one that emits fumes from the tank to the carb) as a return line. Got rid of all that crap that sits on the top of the fuel tank and just directly connected that line to the top fo the tank.
This way, when car is at idle, you have vacuum to open the loop and return fuel back to the tank. At full boost, it will force the loop closed and raise the fuel pressure to your carb. With this system and your Holley Pump, you should have no problem overcoming your boost leanout. As long as you do not boost more than your pump.
I was running 10 lbs. of boost on a 14 psi ProComp pump with no lean out.