Timing lights were invented to set timing. Vacuum gages set carbs. Sounds stupid, but truth is truth. You need maximum effciency at cruise, not idle. Make sure the vacuum advance is disconnected. Make sure that it is normally connected to ported (no signal at idle) vacuum. What carb is it? When you changed the cam... did you re-install the same intake? It sounds like it's not tuned right, but it could be a vacuum leak. That cam should idle lower, and still give decent vaccum. Was this engine ever rebuilt?

Well, art is art, isn't it? Still, on the other hand, water is water! And east is east and west is west and if you take cranberries and stew them like applesauce they taste much more like prunes than rhubarb does. Now, uh... Now you tell me what you know.