Possibly the wastegate solenoid sticking shut. Google gc8 "check connector" to find how to set up the sensor check mode for your ecu - then see if you can hear the solenoid clicking open. This is a good time to spray it with carby cleaner to remove any internal sludge build up.

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[CENTER][COLOR=#ff0000]Built Ej207: Semi-closed RA Cases - Wiseco Forgies - Manley rods - BC 272 cams - GDA Heads - billet f/whl - Vi-pec - WbO2 - 800cc Yellow tops - TD05-20G - 409Hp ath @ 1.75bar on E85[/COLOR][/CENTER]