I do these tests with a vacuum gauge and a "tee" on a twelve foot section of the hard vacuum line used for vacuum door locks.
I watch the vacuum as I drive (I do this in controlled conditions - BE CAREFUL). One should tee to the line going to the trans for the final overall control signal. This should be high vacuum at idle and drop with throttle rotation linearly to about 3-5 inches of vacuum at full throttle. This can be varified with a quick snap of the throttle. The smoothness of the vacuum transition (from 15+ to 3-5 in. vac)is much easier to see during easy rotation of a medium acceleration on the road or dyno. Once the throttle is full, boost will build (this should be verified at the line to the "blue" amplifier; boost signal should be verified to be complete 0-9/10 psi). As the boost builds the vacuum to the trans should drop from the 3-5 inches to zero as bost reaches maximum.
That is what it should look like. The reason the amplifier has this signal profile is because it amplifies the original trans signal that used to go to the modulator before 1985. This signal comes from the prepared signal at the proportioning valve at the rear of the injection pump. It is something that also should be checked if the end signal isn't reliable.