the size of the idle jet can be a big deal on these carbs. i would think the more plenum volume the more critical this can be off idle. i don't think the passages from the jet to the main wells in the edelbrocks are as large as the old afbs. comparing emulsion tubes on the edelbrocks to the old afb/avs is an eye opener for race builds. the edelbrocks and older afbs have a lot of places where they introduce air in the fuel stream and some of that can be blocked in a race car. juggling the secondary opening rates with the velocity air valves is kind of trial and error. an avs top would make these carbs more ideal for performance, but edelbrock won't sell tops seperately.