Your system is early emissions incorporated into the last of the 113 chassis.
This basically means decel fuel shut off and controlled retarding of the timing via temp switch/speed relay/trans sw/ and idle switch.
The speed relay has 2 speed circuits, one for decel and one for vac valve.
There is a sequence of test for proper operation and these are covered in the Haynes Manual # 346. Should be able to get at any decent parts store for $15-20.
If not , I can scan the procedures for you , but it will take some time...
The basics are the vac transfer valve is looking for voltage
above 2400 rpm, [ advancing dist] no voltage below.[retard].
The earlier 113 simply used vac at idle/closed throttle fed to the vac retard servo on dist. So as throttle opened, less vac resulted in more advance [ actually, less retard]. from there, the advance was only mechanical .]