Richie: Ok you are running a 600 cfm El. was it out of the box. If so it should be st up to go if not then you might have a accelerator problem but I do not think so.
My recommendation would be a Edelbrock Performer Series fuel pump #1721. You need to maintain 6 psi for street use and a little fun. I am not a Holley fan it sounds like something is getting weak. What it all boils down to is you have to correct the pressure. Where is your filter, newer vechiles with in tank filters have also ran into this sort of problem. popcorn The Truth is Out There (Good Luck)