I think the vacuum at the vavle should be constant.
The transducer is activated by exhaust pressure. As the exhaust pressure rises, the transducers opens the valve to the vaccum line to allow it to open the EGR vavle. The transducer is variable, but I don't believe the vacuum from the manifold to the vavle is variable.

1995 Trooper LS auto 3.2 DOHC /w SOHC intake
1989 Trooper 2.6 auto
1989 I-Mark RS DOHC 1.6
1991 Stylus XS DOHC 1.8