Argh! Stumble off idle with new parts?!

[Kixwy2]

So I have a brand new crate engine, a professionally rebuilt Rochester quadrajet carb, new fuel pump, new accelerator pump, and mostly all new parts in my car. Engine is timed at 10* BTDC and fast/slow idle set to recommended specs.

Engine runs like a dream, except for the stumble off idle. Damn. I have narrowed it down (I think) to my fuel mixture being too lean, but I need some opinions and advice to be sure. And I forget: is turning the screws in clockwise = more air or more fuel?

...This is where the Haynes manual fails - "adjust mixture as necessary." Er, ok, great directions there, Lou...