They are not exactly ON the playfield itself. Two are located directly behind de shelter scoop on two small red starposts. The third one is located on the upside down small red starpost above the yellow popbumper.

ES.jpg

I think the white sleeve is shown in the picture above as a yellow one. At the left side on the entrance of the center ramp.
On my machine this tapered post sleeve is also yellow. This is more in sync with the colors of the plastic above the post and the zone 4 target on the right of the ramp.
No idea however why this one sleeve needs to be tapered other than ball control on high impact...

I know....mine is also still in parts broken down. Hope to touch up the pf this weekend and glue the inserts back in for clearcoat. Afterwards applying decals and another two/three layers of clear.
then...than starts the replacing of all pf stuff... A ton of work but in the end all worth the time and effort.
keep us posted on your progress, maybe I learn something new from you

I just found three more white grommets on the playfield... This is a photo taken from my own ES before removal.
Since they are actually on the playfield I much more think that these are the grommets Williams mentioned in their listing of rubber items...

white grommets pops.jpg