For primary diagnosis, it is quite easy for the DIYer to isolate the vac/mechanical side of the system from the electrical without gauges and pumps, etc...
Simply unplug the green plastic line at the SOV from its rubber hose . Now unplug the rubber vac line on top of the SOV.
You can now insert the plastic green line into the bubber SOV feed line you just disconnected..
This eliminates both the SOV and the electrical system circuit.

Next morning, cold car, go down the road and see if you have delay...
If you do , you problem is electrical [ signal feed to SOV]
If you don't , you have a vac/element/actuator problem...
As soon as this test is done , simply pull over and plug the lines back in the original nipples/hose....

This save much time/thought as it gets you immediately to the fault side of the system for further testing..
After this test , I would then verify the SOV operation as the next step w/manual voltage source.....