After fixing a 'up-until-recently-unknown' vacuum leak, I tried readjusting my idle mixture screw adjustments and I had a question.....

This is on a rebuilt stock 383 (low compression - no more than 9.5/1 and probably a little lower) with a Edlebrock 1405 that had been jetted down 2 sizes (before I did that the exhaust was pretty rich with unburned gas) Previously I had noticed that at around idle the idle was never very consistant- it would vary about 40-80 rpm randomly. I had hoped/thought that the repaired vacuum leak would remedy this but no dice, and with this going on it's a bit of a challenge to get the idle mixture adjusted.

Is there something else going on that I need to look for, or is this 'as good as it's going to get' for my setup?

Thanks!
David