have you ever seen this before

Typically they "run-on" because the throttle blades are open too wide at idle and it is pulling fuel through the main venturi instead of just the idle circuit. The throttle blades are probably open too wide because there is not enough initial timing, so the throttle has to be open further in order to idle. It also sounds like you need to set the float levels.

Contrary to what some people will have you believe Holley's are actually very simple to tune, and stay in tune just fine.

Start with finding out what the initial and total timing is and set the floats.