[scottj]

It sounds like a part-throttle lean-surge which is a common problem when running larger cams in street applications. The idle circuit has a major influence on drivability at very small throttle openings such as slow cruise and light acceleration. Fuel mixture, at throttle openings from just off idle to the point where the boosters come in, is controlled by the idle feed restrictors and the idle air bleeds. Idle mixture is controlled by the idle mixture screws. Generally, cams that produce low vacuum need enrichment of the IFR/IAB to help a lean-surge condition.