Matched carbs, means the tags match, so you know the jets and venturie are the same. Sync, is measuring the flow through each carb with a manometer, a unisyn, to be sure that both are doing their job the same. They get in sync with the linkage loose.
Here is the link to a great article. Jon, the Carbking posts here often. He's extremely knowledgeable, and a nice guy- I spoke to him on the phone one day. Its a great read. I found it very helpful when working on my truck. I had originally followed the instructions that came with my offy manifold, but they were wrong about the mixture and such.
http://www.thecarburetorshop.com/RochestermultipleB.htmA vacuum reading will tell you alot in a situation like this. It's like a window inside the manifold.
Some of them "hotrod" cams have lash specs of their own.
