I have a 454 L29 Crate Engine with a 4 barrel Holly 750 Double Pumper and Holly blue fuel pump (no fuel pump boss). The previous owner had the fuel pump mounted upside down and the thing was cavitating & failed shortly after I bought the car. I replaced the pump a regulator. Now the fuel pressure is not controlling properly. It starts out high at around 9 psi and drops to below 6 psi after driving a while. A few times it dropped to around 3 psi, and I closed the regulator, but could not increase the pressure. I changed out the carburetor, and that didnít help, I made sure there were no kinks in the line, replaced the fuel filter. The pressure gauge is mounted on the line going to the secondary bowl down stream of the regulator. When I punch the gas, the pressure does not change. I have checked the grounding of the pump and it is getting 12 volts. The pump is wired through the fuse block i.e. no relay is used. Any ideas/suggestion are appreciated.