This is driving me crazy, I need some help!!! I am running the same combination in my 67 for quite a few years now without any problems. It is a mildly built 350, 4 speed with a Holley 1850 600 cfm vac secondaries. The car sat for a couple of years with some treated fuel in it. I have recently started driving it and had a fuel starvation problem where I almost didn't make it back home. The old pump was all wet on the outside and I figured that it was going bad, so replaced it with a new Holley mechanical unit and installed a see through filter and pressure gauge between the pump and carb. Fired it up, filter is full of fuel and 5.5 psi, then it slowly starts loosing pressure until it wouldn't stay running. Figured it must be the sending unit, since it was the original one. Pulled it out and the filter/sock was all deteriorated so I thought that was the problem. New tank, new sending unit, new steel line from tank to pump and all new rubber fuel line sections. Fire her up and same problem. Has to be the pump right? Summit sends me a replacement. I install it and same problem. I fire it up, 5.5 psi and fuel filter is full of fuel, but it slowly starts loosing pressure and volume. What the heck is the problem. The carb is the only part of the fuel system that I have not changed. So does it just need to be disassembled, cleaned out and rebuilt or is the problem somewhere else?!?!?