Just read your suggestion and this is what I had been up in the shop doing (though I sprayed with carb cleaner to clean).

I still could not get this new Firad nozzle pin to gravity-drop all the way into the nozzle. Nor would the nozzle spin on the pin when held horizontally by the top of the pin.

Just to see what would happen, I swapped out the new Firad in this nozzle for the Bosch (that I had driven about 20 miles on). This one gravity-dropped & spun perfectly. Put that in and I STILL GET pre-pee. This suggests to me that it is not the nozzle that is allowing/causing the pre-pee.

I had actually done a good bit of lapping on this nozzle (600/1200/2000) and am hesitant to remove more metal. It looks smooth...though there is some pitting in the bottom face of the spacer.