When it doesn't work there is no turbo wine. I know the turbos are not working. Is issue is on and off, it must be a sticky wg or boost controller. Any idea of location for this car?

HI I’m new to this forum. My wife's XC90 T6 is not building boost. I know a bit about turbo engines so I wanted to know possible causes from you guys so I could fix it No check engine light, so I think is mechanical issue rather than electrical. Does anyone have a diagram of the turbo system? lookin...