Idle and decel should be around -20 to -25 inHg possibly even as much -30 inHg in decel at moderate to high RPM.
Partial throttle should be around -10 to -15 inHg
Full throttle should be extremely close to 0
And just for reinforcement of theory. The engine will always pull the same amount of vacuum for a given RPM. The throttle plates position it what limits natures ability to equalize the cylinders back to 0.