VNT actuator on BNV 1.4 TDI

Hi,

I'm trying to diagnose lack of boost on a 2008 1.4 TDI with the BNV engine. I've worked out that the VNT actuator works in the opposite direction to all others I've come across in that it pushes the rod out which springs back rather than the way more common pull type. Also it appears the actuator needs positive pressure in the pipe rather than the usual vacuum. Looks like the actuator and VNT mechanism are fine as the VNT lever moves easily and the actuator rod moves out under pressure (from a bicycle pump). But there's no movement when connected to the valve block. 

The valve block has three connections that look relevant - numbers 1,2,3 which are connected to the pre turbo intake air pipe, the VNT actuator and what looks like a tap off the turbo outlet (boost side) pipe flange.

So the question is, where does the positive pressure come from that is supposed to push the rod out and hence move the VNT lever to the higher boost position?

I have VCDS and have run the basic settings test. There is no change in charge pressure when the VNT is on or off and the rod doesn't move at all.

I have a huge amount of experience with the 1.9 TDI PD engine and know the VNT system inside out on these, I'm just confused and can't find any information on this 'reversed' system.

Thanks.