Edelbrock Owner’s Manual covering Performer and Thunder series carbs- HERE
. With the info from it and from Edelbrock Performer Series Carburetor- Complete Guide to Set-Up, Tuning, and Performance Jetting
, you can go about adjusting it for better performance.
Be sure the accelerator pump is discharging the instant the throttle is moved. Changing the step up springs on the metering rods won't help the symptoms you describe.
If you're using a vacuum advance hooked to manifold vacuum, you might need to use ported vacuum. See if it likes that, if it is sluggish you might need to add some initial (and take away some mechanical to keep the total where it should be), if the engine acts like it wants more initial when the vacuum advance is switched to ported.
You may be able to adjust the vacuum advance can (if it's adjustable) to work w/manifold vacuum, this is a trial and retrial type of deal. More http://www.crankshaftcoalition.com/wiki/Hot_rodding_the_HEI_distributor#Vacuum_advance]here[/url]. The page is about the GM HEI but the advance info is universal.