Be sure the issue is not due to a faulty boost pressure sender. Remove the turbo, complete with the catalyst. There is probably no need to separate them. Ensure no dirt enters the turbo, especially the oil inlet. Refer to header picture for part names. Check the wastegate hose for damage or splits. Disconnect the hose from the compressor housing. Blow into the end. If air flows, the diaphragm in the can has failed and you need a new turbo. If the pipe and the diaphragm are intact, use a footpump with a lilo inflating adapter to pressurize the actuator. The rod should move by 15 psi. Don't put too much pressure on it as you will rupture the diaphragm. If the rod does not move, or it moves out and not back when the pressure is released, it is sticking. Don't worry if you find oil in the hose.
Repair
Undo the two screws holding the actuator bracket to the compressor housing. As they are loosened the rod will be drawn into the can by the spring inside. Do not undo the locknut on the rod, if you turn the adjuster you will lose the calibration. When the can is free carefully rotate it on the rod until it can be moved sideways. This is not good for the diaphragm, so keep the rotation to the mimimum. The compressor housing is now vulnerable so put one of the screws back in to make sure it does not get dislodged in the following process.
If the wastegate is stuck in the turbine housing (unlikely), separate the catalyst from the turbo and investigate.
If the rod end is tight on the crank pin (more likely), work the rod around the pin back and forth as far as possible. This will loosen and expel the corrosion that has caused it to stick. When it is completely free, remove the temporarily installed screw, place the actuator back in its correct position and rotate it back to align the bracket with the compressor housing. Refit the two screws. As they are tightened the actuator moves back into position, tensioning the spring as it goes.
Use the footpump to check that it moves freely. Reconnect the hose to the pipe on the compressor housing.
Refitting
Refit the turbo to the engine. Before connecting the oil inlet prime it generously with oil. When first starting ignore the glowplug light, crank immediately. This will prolong the cranking time, allowing oil to fill the feed pipe before the engine starts. When it starts, do not rev. Allow to idle for 30 secs to establish the oil flow before increasing the turbo speed too much.
