UPDATE
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Dealership copped out from replacing the DV valve!!!
The dealership informs me that VW HQ now insist that readings are taken when the car is being driven for warranty claims - and to no surprise the results collected were totally out of kilter from the ones on a stock VW. So there's no way of hiding the fact that the car has been remaped.
Anyway, I'm fairly certain the dealership aren't trying to pull a fast one. They replaced the pressure valve (still don't know what that is) Apparently that was an easier warranty claim, as it has a VW recall.
So, today I got the Forge re-circulating DV fitted - and by God it makes a big difference. Boost is definately back... and the engine and exhaust are roaring like a tiger!!!
As you can see the original OEM DV valve (revision G) has a torn seal...I'm surprised the car was moving at all.