Slight miss in my 69 Z28

[sixt9rsx33]

At idle my car has a slight miss/stumble. This issue does not occur above idle or at acceleration. The car will idle at 900 and the tach will drop to 700 or so. The drop is almost undetectable by ear or feel. I hooked up another tach to the car to confirm that my tach was not going bad and had the same result. I suspected bad plug wires those checked out ok. I cleaned the distributor cap terminals. (I have not changed the cap yet, it looks ok). Spark plugs are good. I recently replaced a bad condenser. The points have not been replaced. I was thinking that there may be trash in the idle circuit of the carb since the problem is only at idle. Is this a possibility? Any ideas are appreciated.

Thanks

Lawrence