I think the short hose should go up on to a connection on the throttle body.
Cant remember for sure but it shouldnt be just loose.
That may be the cause for the problem or in my 84"s case it was a gunked up air bypass solenoid. It is conrolled by coolent temp switch/lambda sensor/output from the coil and a switch in the throttle body. I would suspect, if this solenoid is the problem that when you let off on the gas the switch isnt activating so the ECU
doesnt open the air bypass solenoid... so it is getting zero air. Have someone press on the gas pedal with car off/ you can hear the switch on the throttle body.
If not it needs to be adjusted or you need to clean the throttle body so the flap can close all the way... it may be hangen up..
Just a thought.
On my bus page there is a link to pics of what I have done on the 84 200.
Might help
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vw bus site - http://www.geocities.com/vw_bus_74/index.html