A little bit of closure on this, I've also posted it up in my project diary.
As above, the part in question is a thermo-pneumatic valve, and it controls whether or not the the secondary stage of the throttle can activate. It's connected up via the green hoses in the below diagram:
Below 28 degrees the valve is open, which means the secondary stage throttle can't activate as no vacuum can be held. Once the valve heats up above 28 degrees it closes, the secondary throttle stage system can now activate as vacuum can be held. Apparently this valve was only fitted to 1.6 litre manual and 1.8 litre automatic cars built after 1984, but I've fitted it to mine in the vague hope it may help solve the problem of my car cutting out when the engine is cold and the throttle is opened up.
Credit to Rubjonny's excellent Prierburg guide for the above information btw, as that's where I read up on this :)
I've no idea what these connection are and what they should connect to, they're not present on the Golf. Are they vacuum lines?
