Its most likely you are too lean at idle and transfer so you have to advance the timing to improve the fire events at idle to create enough vacuum. What do you have for IFR's and IAB's? You can partially block the IAB's with your fingers and see how it responds to a richer mixture at idle and on the T-slot as you bring the revs up while out of gear.
IMO you do not have enough compression with 160. I would aim for 185.