Full chassis just in case it helps;

WBABK82020ET80862

Where is the valve?

It does not appear to be under the manifold (Autodata)

Nor does it appear to be on the suspension turret near the air filter (Haynes Book of Lies )

There is what appears to be a charcoal canister to the rear of the engine beneath the inlet manifold which has one vac pipe going to a port below the throttle body. The other disappears into the base of the fuse box. Initially I thought they might have been daft enough to hide the valve inside this but the pipe seems to pass through into the passenger footwall and from there I know not where! (I have not traced it further)

Any suggestions??

(The car is a convertible if that makes any diference)

(Also, would this fault prevent the ECU from entering closed loop, since that is the other problem)