basically the waste gate system is stuck or has failed. if you can get under the car, check at the actuator. the lever that it pulls might be seized.with a small pair vise grips attached to the square lever you should be able to move it up and down about 2-3 cm or about an inch. if it's seized you can sometimes free it up by spraying some wd 40 while moving it. if it's bad it will take quite a while before it gets loose. if it does free up, apply some anti seize by brush [make sure you get it right into the mechanism] or with copper anti seize spray.
if it's free already then check the hose that runs to the actuater to the solinoid. check all the other hoses to the solinoid also. if that doesn't work either the solinoid isn't being triggered or has failed.
worse case scenerio is the the turbo itself has failed and you'll need to replace it.
if you do and whoever changes it doesn't need the core i'm sure me or someone else on this forum would buy it.