Fluctuating Idle only while coasting?

I have a 92 Civic VX. I have been chasing the bouncing idle for a while now. I have followed the coolant bleeding procedure from Erics youtube video. I have replaced the IAC valve with an OEM valve. I have replaced both the PCV valve and the hoses and o-rings from the breather box. It has reduced it some but it still bounced quite a bit but only while coasting in neutral. If I come to a complete stop the idle will settle to about 750-800 rmps and remain steady. I have no problem when under acceleration or if decelerating in gear. If I put the car in neutral while coasting to a stop the idle is all over. No check engine light and otherwise seems to run well. What can cause this to only occur in those conditions?

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