The CA-2300 is basically a product to help the 4 cylinder performance customers with their engines.  The EFI lower intake is far superior to the regular carburetored intake.
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The CA-2300 has fins on the inside to direct the airflow from the Holley 500  to the 4 holes in the lower portion of the EFI manifold.  Others supply a spacer, but the 2 tall spacer from PME really puts a boost in your power and performance. See picture below for complete kit.


Bottom of adapter

Theirs verses ours.