Proform 850 dialing it in closer

Pulled the metering block off that hasn't came off sence installed new last year.
Its not a 5 hole but a 4 hole and the brass jet is a plug and the open jet holes are pre drilled holes.
so i could plug one of the 3 remaining holes to see if it smooth out the o2 reading(Saw tooth affect)
But were do i find jet plugs this small?

Do i Plug the top hole or 2nt one down?????

I pinned the holes, but don't have any way to read/measure the pin so will have to go to work to do that, in the morning.

IMG_0474.jpg IMG_0477.jpg