Odd minor idle issue, slightly fast until it's not Options

[oakdalecurtis]

76 2.0 FI stock except for Crane ignition. I finally got all parts dialed in, AAR, thermostat, no vac leaks, runs perfectly, just passed smog with best numbers ever. It idles at about 700 rpm after warmup, but sometimes when I get to a stop light and come to a halt, the idle will drop to about 1200 to 1300 and hold there. If I let the clutch out slightly to drop the idle further, the idle will then drop the it's typical 7 to 8 hundred and hold there fine. Any idea why the idle would stop sometimes at this slightly higher speed sometimes? It can't be an air leak or the idle wouldn't go to 7-800 most of the time, nor would slowing it further when it's at 1300 rpm get it back to it's normal idle again. Not a big deal, just curious if the wizards of smart in here have any thoughts on what to look at. Thanks