Actually, Holley doesn't say anything one way or the other regarding a lean or rich last adjustment, however, the idle mixture screws are only effective on the idle circuit. Going 1/2 turn lean always gives me the best results. Do you want your engine to puke out gas smoke and burn your eyes because it's too rich at idle? Adjusting a tad lean affects nothing negatively and might even save you a little gas. But adjust them how you see fit.
Yeah that was my bad, edelbrock says to turn it lean after adjustment just enough to drop the rpm by 20 i was thinking it said to richen it up after but i read it wrong