232 engine heat control setting

I don't think it should be closed at idle, and moving at all w/ revs!  It should be based on the temp of the engine, not the RPM.  It should be closed when the engine is cold, so the exhaust gases heat up the intake manifold rather quickly, preventing the gas in the fuel/air mixture from condensing into droplets.  As the engine heats up, the thermostatic strip should gradually open up so the exhaust gases go out exhaust pipe instead of heating the intake manifold.

I would say to make sure it has correct tension, and closely inspect the bimetallic thermostatic strip to make sure it's not cracked/damaged.  I think you can still buy them, but they are probably listed under other makes.