My D-Jet is on a '72 VolksPorsche 914.....had idle hunting problem until I backed all the way off of the air bleed--like to slow down the idle, which is counterintuitive, but was necessary to allow the system to control itself properly. First start would give the appropriate high idle for about 30-45 seconds, then drop down and back up--hunting between 150 and 1000. My first action was to open the little bleed screw to increase the idle speed. No help. So, after making sure that there were no vacuum leaks anywhere in the system, I closed the idle trim screw down all the way and then only opened it a small amount. Voila, the thing settled down to a nice steady idle!

Good luck--let us know what you finally find out the culprit is!