Ported vacuum SHOULD NOT be present at idle. If it is, you've got the throttle plate adjusted too far open. Try reducing the throttle plate angle, and drill a small hole in the throttle blade if necessary to bleed enough air to let the engine idle properly. The vacuum doesn't need to be on the vacuum advance until the throttle goes to just above idle in most cases, to reduce the tendency to bog and stumble when transitioning from idle to part throttle.
There should be a way to adjust how much fast idle you get when the choke is closed, either with a screw, or by bending the fast idle linkage. Make sure the fast idle cam isn't worn, or sloppy to the point it doesn't open the throttle when the choke is pulled.
The idle mixture screw is adjusted by turning it clockwise (with the engine fully warmed up) until the engine stumbles or misses, then opening it up until the manifold vacuum maxes out. Any further richening to prevent a tip-in stumble should be done 1/8 turn or so at a time until the best compromise between good idle vacuum and throttle response is achieved.
Jerry
