there is a vacuum part on the dash behind the brake booster. It has a vac line to it and from it and an electrical connection. the electrical connection was unplugged. I cleaned the connector and pluged it back in with no perceptable difference

there are two relays under a black plastic cover on the drivers side inner fender. I unplugged these and the one closest to the firewall was severely corroded. I plugged and unplugged it several times and it is now clean too. what do these do and is it better to leave the vacuum part unconnected electrically? pics below