It's asking for a bigger fuel charge Burg's, in essence there isn't enough fuel to "go around", the charge being too dense to reach all cylinders, so you are probably only getting ignition on those cylinders to which the fuel air mixture flows most readily.
As the motor heats up the mixture atomizes more readily, this expansion is a result of heat build up, which offers a better fuel charge flow to the lean/starved cylinders, thus the gradual improvement in engine performance.
I run twin Holley's but only one of them has a manually operated choke, which is more than enough to supply cold start fuel needs.
