383 Wont Idle with new to me 800cfm DP. Idles and runs ok with Edelbrock/AFB

i have a fresh 383 bored .060 over. New old stock direct connection 11.5 to 1 forged pistons, Mopar 292 .509 cam. Holley street dominator intake manifold. 906 heads with bowl clean up and port matching. No real porting though. When the motor was completed I did not have a carb for it so I dropped an old 600cfm Edelbrock carb I had sitting on the shelf. It starts and runs well. Has a healthy sounding lopey idle. Decent drivability but really giving up a lot on WOT power with the small size.
I picked up an 800 CFM DP yesterday used but very clean. They said it had a kit put in it. I did take it apart and look and it has fresh seals and gaskets and is very clean inside and out. Front jets are 70s. I was unable to make out what the rear jets were but I believe 70s also. I put it on and started the car up. It would not idle at all. I could turn up the idle to approx 1800 and it would hold it. I slower turn the idle screw back until it gets to the idle circuit and it dies. I have adjusted the idle mixture screws out up to 4 turns and no change. I am thinking maybe power valve is set for too high of vacuole and maybe my 7 to 8 inches of vac is causing it to dump. I did not see any vacuum leaks. I have since removed it and put the Edelbrock back on and it is back to running normal. Is this a case where drilling holes in the throttle plates is in order? Thanks for the replies.