serious carb issues

It sounds like you already have holes in the throttle blades? If so, you probably don't need them with a 4 corner idle setup.
I just ran into this on a BBF I built for a customer using his "modified" carb. I could close both front and rear blades and it idles at 1400rpm.
I epoxied the holes up, opened the blades up some and now it idles at whatever I want it to. This was a mild 500HP build, so with a 4 corner idle carb it didn't need the holes in the blades.
That's what it sounds like is happening with your carb to me anyways....
Brian