Still working on getting my impreza running, but we're getting close. We seem to have lost a place for 1 part though and cant figure out where it goes. any ideas?

Looks like the bottom mount for the A/C compressor. It should bolt in down on the bottom, on the driver side. There is a spot in the top of the head on the driver side that should line up with that hole out on the end.

yep, +1.

perfect thanks!

If the AC compressor is already installed you'll have to unbolt it to install this.

 

Also the long bolts can get a bit cramped/bad clearance when doing this.