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

Any situation where the idle screws are ineffective,the idle screw is turned in too far,uncovering too much of the transfer ports.
By settiing idle mixture screws at 2 to 2-1/2 turns and adjusting timing to get idle where you want it then tune from there.
Just had one a week ago that was terrible rich at idle,mixture screws were out 4 plus turns.
Backing off throttle stop screw and adjusting timing as i went i managed to get it to where it would idle nice,and idle mixture made positive changes.
I’m no expert,but i stick with what works. Holleys are great once you get an understanding of them.
I prefer the eddy’s myself.