Putting P5 back to stock, header question

[PBW_Pro5]

I am trying to put my P5 back to stock, and I was test fitting all of my old parts to make sure I have everything. I have a spongy ring that I believe goes between the manifold and cat. Can anyone confirm exatly where this ring goes. When I hand fit it out of the car I can barley get the manifold on, with this ring inplace. Should there be a grove that this fits.