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

More information:
Although I earlier stated that if I "tap" the throttle, it sometimes slows the idle, it is not exactly mechanically connected. It seems that the sudden increase in RPM causes whatever is sticking to loosen, not the throttle itself.
In short, the tapping of the throttle does not directly influence the idle speed. I will check the seals and butterfly as posted. Hopefully this will help.

Thanks guys,


jeremy
--
71 142E and a yard full of 240's in Mass.

Solder the decel valve in the throttle plate closed to eliminate it as a cause.
Check all of the usually brittle hoses to and from the auxiliary air valve. Clamp them up tight.

The air bypass valve usually just sticks in some odd position (sometimes open, sometimes closed). If you wanted to eliminate it as a suspect, just plug one of the hoses - it pulls filtered air in from in front of the threottle valve, and releases it behind the valve.

It sounds like an air leak somewhere in the intake system to me. I'd double check that the throttle valve is able to close completely - when they get worn or if the valve disc gets loose on the shaft it will tend to hang open slightly.

Other than that there are the various fittings on the manifold - for example the brake booster - it could be leaking and sucking in air. The manifold gasket on the head. The injector base seals.
--
I'm JohnMc, and I approved this message.

Are your throttle shaft seals in good shape? How about the hoses on the aux
air valve? To me the symptoms REALLY sound like a loose butterfly, because
that is about the only thing that tapping on the throttle would affect. Or
maybe some dirt or other obstruction that keeps it from closing all the way.
(I sucked a wire into mine approaching a toll gate on the turnpike once and
it did that.) Maybe something getting under the throttle stop and keeping it
from closing?

I'm sure that when you find it you will kick yourself!

Best regards!
--
George Downs Bartlesville, Heart of the USA!