The internal Return (hold Shut) spring on the actuator may have deteriorated An inevitable occurance.
BUT it may not be what yer problem is.
Suggest doing a Base Boost Diagnosis.. as specified in the Bentley Manual (use the C900 one).. identical procedure.
You might also try a 'helper' spring on the actuator.. a simple inexpensive spring bodged between the Actuator and the Wastegate Flap rod (which incidentally Has no resistance whatsoevrr designed in).
BUT it may not be what yer problem is.
Suggest doing a Base Boost Diagnosis.. as specified in the Bentley Manual (use the C900 one).. identical procedure.
You might also try a 'helper' spring on the actuator.. a simple inexpensive spring bodged between the Actuator and the Wastegate Flap rod (which incidentally Has no resistance whatsoevrr designed in).