How do i change when the secondaries open up on my edelbrock performer carb?

my cammed 355 does not pull much vacuum so my secondaries do not open, how do i change when they open, i have heard about metering rods and other things? also where can i get a manual choke kit to remove my electric choke|||You have to change to a lighter spring to get the secondaries to open sooner.|||I would change your carb to a holly650 doubblepumper .This carb is linkage for primary and sec.Which means no more hesitation.|||you should have gotten the Edelbrock carb with mechanical secondaries, I don't like vacuum secondaries.