Distributor advance springs

The vacuum amp is probably for EGR. My Mazda works like this. Manifold vacuum goes into the top or bottom port while ported vacuum goes into the port off to the side and the load (egr valve) goes off the port opposite the manifold feed port. It's sort of a switch that allows a high draw valve (egr) to be operated by the relatively low ported vacuum. The ported vacuum is routed from the carb through a thermo valve (maybe on radiator?) to the vacuum amp so the engine has to be warm to trigger the EGR system. Seems to work fine on my truck after I chased all the leaking vacuum pods. (Egr, throttle solenoid,gulp (anti backfire) valve, evap shutter, distributor...) Every one of them was leaking!