too high compression?

The venturi vacuum port should be pretty high up the bore-wall. It should show zero vacuum at idle, and not start signalling until the throttles are quite far open. The vacuum should steadily increase, then start falling off. It should never reach manifold vacuum. That's why it requires an amplifier which is supposed to follow lock step to the venturi signal, just with more power to operate the EGR valve.
Good luck.