Was tinkering with the idle adjustments the other day.  Set the idle mixture screws at best idle, and then played with the idle speed stop.  I can completely remove the idle set screw and the car just sits there at 900 rpm.  Should I back out the little, hard to get to set screw that holds the back butterflies slightly open?  Have I said lately how much I hate my Holley carb?

The idle stop solenoid is not energized when I'm doing this.  It is wired to the compressor engage switch.

Check  the opening of the secondary throttle plates.  The 4 barrel section may be open a tad.

OK, I backed off the back barrel set screw and now I can get it down below 800 rpm.  Not sure if Holley would like that solution, but it worked.  Holley says that screw should be backed out 1/2 a turn after it contacts the back barrel stops.Don't know where it is now in relation to that.

I was also able to turn the idle mixture screws in about 1/2 to 1 turn for best idle.