What is this part? Air intake idle control valve

[ClassicCamper]

Saw this on the bay and wondering what it is/does..

http://www.ebay.com/itm/VW-VOLKSWAGEN-PORSCHE-BOSC...mp;vxp=mtr
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1973 412 Wagon
1976 Westy
1978 SB Vert

[ClassicCamper]

Any ideas
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1973 412 Wagon
1976 Westy
1978 SB Vert

[raygreenwood]

Deceleration valve. It was used on late autokatica. Also requires a relay/logic circuit. It used a combination of vacuum impulse to tell it when to add air for deceleration....and on automatics also had input from a pressure switch on the transmission to tell it when it was "allowed" to operate. Ray

[KTPhil]

Deceleration valve and two-way valve. Part of EGR system maybe?

[raygreenwood]

Yes....I think on some cars,with EGR this same valve may have taken part in the EGR loop as well.
Ray