Holley Carb Idle Question

I have a 66 mustang with a 302 bored over, with a high rise manifold and dual quads on it. The carbs are Holley 4160 390cfm.

I can't get it to idle below 1,100. It fast idles over 2,200.

I screwed around with it for awhile, unhook all the linkage, reset everything, and the primary idle screws are backed out.

So after all that, I decided it was time to look at some instructions online. Per the instructions, "This adjustment should be made to both the primary and secondary screws in equal amounts.....".

Huh?

Hell, I didn't know it had a secondary screw. Luckily, it gave a picture of the location on the secondary screw.

I've looked all over the damn carb, I don't know where this screw is.

Any suggestions?

Thank you,

Thank you very much.

I've located the secondary vacuum assembly in the instructions. This will help a ton.

Thank you!