Assuming you did connect it correctly, you should only see the car running badly, or missing while it's at cruising speed. At idle and under full throttle, the vacuum advance should not be a factor. Is that the case here? My car would "miss" at cruising speed, as my vacuum advance was advancing the timing too much. You can use an Allen wrench to adjust the pod so it doesn't advance so much... but I ended up doing what Chryco suggested. If you go that route too, be sure to plug that port on your carb so you aren't sucking in unmetered air.
Mike