RE: YS 160 Surging at idle
If you are getting a surge it is an indicator of a lean condition. I am taking for granted that your idle is around 2000-2200 RPM. Since the DZ fuel system is different from the usual pressurized YS fuel system and the idle is set by the regulator you might try richening the regulator just a bit. I am thinking this might be the issue since you state the high speed needle is set at 2 turns out which is usually very rich for a DZ.