My recollection from the last time I looked at edlebrock instructions (helping a friend) there are two idle restrictions. Otherwise the idle transfer circuit is similar.

My guess is that the cause is the same as it would be on a Holley. If the idle mix screws are not getting any response, then most of the fuel is feeding through the transfer slot. See if you can close down the throttle plates a little. If the engine rpms drop to much to support idle in gear, then try increasing initial timing a 2 degrees.