Don't know a whole lot about them but reading the WSM suggests a couple of pointers:
To ensure an optimum torque curve, a Garrett turbocharger with variable turbine geometry is used. The movable guide vanes on the turbine wheel are adjusted by the turbocharger vacuum canister by means of a connecting rod.
A position sensor is located centrally on the turbocharger vacuum canister; this forwards the position of the guide vanes to the powertrain control module (PCM) as an input variable. The vacuum to the turbocharger vacuum canister is metered by the boost control solenoid valve. The boost control solenoid valve is controlled by the
PCM .
TO CHECK THE ROTOR
– 1. With the turbocharger stationary, gently lift the shaft (the shaft will naturally lay in the bottom of the bearings).
– 2. Make sure the rotor spins freely within the housing.
TO CHECK THE VACUUM CONTROL CIRCUIT FOR VACUUM1. Disconnect the vacuum line from the turbocharger vacuum control solenoid.2. Install a vacuum gauge between the turbocharger vacuum control solenoid and the vacuum line.
3. With the engine at idle the gauge should indicate a vacuum of 0.325 bar (4.7 PSI) or above.
There are other tests but those should make a good starting point.
Cheers
Russ