This scanner recorded data of this C6 shows the reaction time of going from NA to boost coming on

At the bottom of graph you see elapsed time and graph showing torque, horsepower and MAP.

At this elevation of 3,500 feet the maximum MAP can be is 90 KPA ( where sealevel would be 104 KPA) and you can tell then by MAP data when boost came on and this case up to 135 KPA which is -10 inches of vacuum.

Notice that the time boost came on that within 1/2 second torque went from 338 ft/lbs to 474 ft/lbs.