You wont like this post... there is a small spot on the bottom of those cast iron 2 barrel intakes where they burn through. Result is a vacuum leak that simply cannot be found.
If you are exempt from local smog rules, block off the egr and by all means disconnect that electric choke assist and those knox switches on the right side of the firewall. If all else fails, pull the intake. Your local machine shop will hot tank it and weld the burn hole closed. Disconnect the vacuum spark advance, put a cap on that carb port, set the initial timming about 16 to 18 before and happy moparing. Worked for me.
