GM Service Manual Online
For 1990-2009 cars only

Vacuum

Elevation

Minimum Acceptable Vacuum

At sea level

70 kPa (21"-Hg)

5,000 ft above sea level

-57.8 kPa (17"-Hg)

10,000 ft above sea level

-47.6 kPa (14"-Hg)

15,000 ft above sea level

-37.4 kPa (11"-Hg)