Need input from big cam users.

What I am looking for is just what people have seen re vacuum readings with cams. When I say the needle bounces I mean it really bounces !! Is this what everyone sees when putting a vacuum guage on these motors? While I understand that a big cam can cause this kind of fluctuation, I would think that above idle the vacuum should settle down, which it does so to a degree but it still bounces 3 inches or so.