Jeremy,
On my 71 B20E I have been having the high idle problem as well, with the same kick down effect on the RPM if you open and close the throttle quickly.
I have been through everything looking for an air leak and mine difinately is at the throttle valve. I would get the rpm tuned reasonalbly down to 1000 RPM and with my fingers reached in the throttle and manually pushed the butterfly valve completely closed, feeling a "catch" in the seating of the valve with the throttle body as it closed completely.
I have lessoned the degree of air leakage with butterfly valve adjustment but it is tricky, I have some sort of worn seating of the valve in the throttle body that messes up the adjustment.
Try reaching in with your fingers and "feel" how the valve is closing, and whether pushing it closed manualy will lower your idle speed.
North Carolina is an excellent place with 70 degree bright sunshine all day today. You really should get a job transfer. Good luck.
Joel