As a side note on this post the chart is interesting. One of the few places gm uses vacuum instead of map. The right side is the richest so I would assume the 0 column is 0 vacuum equal to roughly 100 map. The left side is 80 and being as it is the leanest there is no way it would be map and it should still be vac. We know vac doesn't go to 80 so the next guess is 80% so then comes the question 80% of what. 29.92? Without a gm tech manual some of this is guessing.