You're running an Edelbrock/Carter carb, right?

If so, your vacuum levels are low due to the big cam and the metering rods are opening before they should.
(Vacuum holds the rods down (lean) shut, the springs open them (richer).

Looking from here I'd say you're running too strong of a metering rod spring.
Try a pink one and see how that works.

Don't go too light on the springs or you'll get a flat spot when the secondaries come open.