Thanks for the reply.

He has just bought the car around 2 months ago. It has 36k miles from new and we thought it was standard with just stainless exhaust. We have had a look at the ECU and it is labelled as 'Stage 1' but performs a little weak at the minute.

The actuator look pretty new, but we have tried a second one which made no difference. Cant see/find any vacuum leaks, and the car has ran like this since he bought it. Looking through the receipts, there is some their for the actuator, one for a MAP sensor etc which suggests that a previous owner has had similar problems.

Checked the DV and that seems ok, and cant seems to think anywhere else that could be leaking boost other than Actuator or DV.

Its as if the engine isnt detecting enough load to provide low boost. Could it be earthing problem??

Starting to anoy the hell out of us.