If you are at 800 rpm your mechanical advance maybe coming into play. Its normal for the rpm's to go up when you hook the vaccum line back up. Just close the throttle plates up to the slow it down and than adjust the idle screws. You need to get the idle and throttle plates right before adjusting any thing else.The edelbrock requires alot of piddling if it doesn't run right out of the box. Also the vaccum can may need to be replace with an adjustable one. To much vaccum at cruise and it won't drop off fast enough causing it to ping. A spring change on the metering rods may help also. Running the manifold vaccum for the street will help the engine to run cooler, esp. at idle.