There's only one Air-Gap intake. Edelbrock makes a "RPM" manifold. They come in 2 styles. "Ait-Gap" and regular w/heat cross over cast in.
Other intakes by Edelbrock may also have a "Air-Gap" due to there racey design. AKA Victor series intakes. Big block Chrysler's are natural A-G designs from the factory.
Check the idle screw on the carb and the fast idle screw. Due note when you tap the gas, if the choke closes a tad in-acting the fast idle setting which would cause the idle to jump up.
