Mark, I looked for the foam for quite a while then discovered that it came with the AC A279C filter. Bought the filter at a local parts store. It is ironic that GM charged $7 for the HD airfilter option and the AC A279C cost me $6.11, including the filter and foam when I last bought it 3 years ago. I don't know of anything additional the option got you but the foam around the A279C. :rolleyes:
If I remember my, long ago discarded foam, (they now call it polywrap) it may have been light colored where the stuff now is dark.