The vac advance is an additional advance to the mechanical one - in other words, the disti has a standard mechanical advance, and the vaccum pod pulls an additional plate to give you more advance in light load situations.
I know on a mopar disti, the pod can just be pulled without doing anything else (the arm just pulls the stop plate more), you probably will have to look at yours to see if that is true on a ford.
Is there a reason for you to pull it?
If you say that it advances too much at idle - you have it plugged into the wrong port on the carb - it should be on the timed vaccum port which should have 0 inches at vaccum at idle and really anything below about 1500-1800 rpm. On a holley this is the port on the primary side metering plate, right hand side, about an inch from the air cleaner. Not all Holley carbs have this port drilled, but they all have it cast.
It is safe to disconnect it and cap the vac port on the carb and disti (carb for vac leaks, disti to keep the water out). This will basically make it a mechanical advance disti.
I have found the vac advance disti's usually are worth more money than the std mechanical ones - you might pocket some cash if you sell yours and get a mechanical rathern than modify. Just a thought.
