These vacuum actuators can definitely fail when the thin rubber diaphragm inside tears after exposure to heat, age, and years of cycles. You can use a vacuum pump equipped with a gauge to test each of the pods, but be careful to only apply a very small amount of vacuum and see if it holds. Applying too much vacuum will tear the diaphragm, and then you won't know if the pod was bad or if it was ruined by the test.
If it turns out that you need a new center vacuum actuator, our Intake Manifold Repair Kit 272 140 2401R-PRM contains an upgraded center vacuum pod that's equipped with a high-temp silicone diaphragm to better resist heat, cycling, and age hardening. Our repair kit also upgrades the center pivot rocker to aluminum with Delrin bushings (the OE rocker is all plastic), and upgrades the actuator rod to durable aluminum (the OE rod is plastic with a small cross section). Here's a
video and a
flyer explaining the kit.
Pelican offers the repair kit here:
https://www.pelicanparts.com/More_Info/2721402401RPRMINT.htm?pn=272-140-24-01R-PRM-INT&bt=Y&fs=0&SVSVSI=5873