Engine shutdown delay???????

Hello community, recently in Switzerland have had an Impreza WRC in front of me, the owner got out of the car, shut down and the engine ran estimated 3 minutes further before he shut down himself. Does anyone of you know what part that is that I have to install???? Of course, for all older turbo vehicles the Turbo is not a good thing. I am grateful for every answer and hope to find the part. LG Autofreak1988