Gents there are three pipes which go through the bulk head to the heater matrix two come from the valves mounted on the nearside wing which I assume are flows for the left and right ?? the other has a valve on the bulkhead then a loop and a return to the cooling system for the supercharger - what does this pipe do ? is it the return from the matrix? also what is the valve?
Sorry can't post pics as car is not here

Sorted there are two inlet (left and right) one outlet and the valve is an isolator for the FBH