what are these plugs that came with my new rotor housings?
 

I got some rubber plugs with a metal insert with my new rotor housings. What are they for?

Those go into the oil injection holes before the injectors are screwed in.

They have a specific way to be inserted and this must be observed. Mazda went to this new design around 1992 or later.

anyone know the procedure? It looks like there is already something in the injector hole, could these be extras?

My new housings that I bought in 2000 also came with those new rubber/brass things but none where in the holes and I had to insert them.

Do a visual to determine if they are already there, or even try to poke out what is in there if you are so unsure.

They go in with the brass side down. They need to be carefully pressed in so they go down flat.