I measured my vacuum at the hose just before the line to the A/T modulator(just after the surge damper and orifice). At idle the pressure reads 14"hg. As I increase the rmp's just slightly the vacuum decreases to 3." So, at only 1200rpm I have around 3" vacuum. As rpm's increase from 1200 to 4000 the vacuum remains at 3."

Does anyone know the proper linear change in vacuum in relation to change in rpm's. I understand that at full throttle there should be nearly zero vacuum, but more specifically how should the vacuum change all the way through the rpm range?