[donut]

Can you "kick" the idle down with a blip of the throttle?
You could still have a bad vacuum leak or the fast idle needs to be adjusted. Vacuum leaks can occur in anything vacuum related, esp hoses. My last bad vacuum leak was actually a failed brake booster.
Fast idle has an adjustment screw on the choke side of the carb, down low. If this is staying engaged it could keep the throttle blades held open.
Keep track of adjustments, I try to write everything down so I have a baseline I can go back to. To many screws, to many adjustments, real easy to get turned around. Also stick with one adjustment at a time.