Probably lost electronic control of the Boost Control Valve. BUT it sounds a bit low for the manual wastegate actuator?
Check the wiring of the BCV. Have you been playing with the boost controller just before it stuffed up? Left any "friends" in the car unsupervised?

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Speak to Shane @ SMC Tyres, Unit 6/385 Sevenoaks St Beckenham WA 6107. Mobile 0413 128 087. Tell him Maddog sent you!