Listen to Sam, he's getting you going in the right direction. There's a lot of confusion in this thread about vacuum canisters/amplifiers. People are talking about two different things.
No vacuum amplifier is needed. For starters, I don't even think the vacuum has even been tested, correct? Get yourself a gauge. They can be had for cheap at Harbor Freight and see what you're getting. 18-20hg is good. 17hg is satisfactory. 16hg and below you'll need to figure out where it's leaking if the engine is a stock build. If your engine has low vacuum, you need to figure out where it's sucking air in at and then fix it. Trying to buy a vacuum amplifier to make up for the engines problems is a losing battle.
The two most common areas for a vacuum leak to occur on a super six is where the intake meets the head and then the throttle shaft of the BBD. There's two fairly simple ways to check. You can spray carb cleaner along where the air could be leaking and listen for the engine to rev up. My preferred method is to spray soapy water all over where air could get through. Then take the PCV hose off and spray some air up through it toward the carburetor. There should be bubbles forming where there's a leak. The leak on my BBD carb wasn't huge and it was tough to tell by using the carb cleaner method. But when I sprayed soapy water and shot air up in there, I could see it bubbling through the shaft bushings. Had the bushings replaced and my vacuum went back up to normal and my car ran much better.
