Bruce Hubbard

The throttle downstream sensors are underneath the air filter box.
The air filter box is a press fit on to three posts
It is unlikely that the air filter box has ever been removed since the car was made
and the rubber fittings will be fused to the plastic posts from engine heat.
Spray some WD40 on the top of the posts and run a screwdriver down the slot in the top of the post and work the rubber free from the post.
The air filter box can then be lifted off the posts with a bit of force. Free the box from the back post first, then the front.
Before reassembly grease the posts and the rubbers to make future maintenance easy.

Remove the top of the air filter box
Remove the air filter cartridge
Remove the three screws holding the intake to the air filter box (careful not to let the screws fall)
Disconnect the battery terminal clamp (negative, chassis earth side)
Remove the two large multi pin connectors to the ECU
Unclip the ECU and lift it up to remove it
Remove the cables from the air filter box

Examine the ECU connectors
If someone got careless filling the engine oil and it ran down, the ECU connector sockets may be full of oil
Spray clean them with MAF cleaner and allow to dry, also the plugs on the cables

The throttle downstream sensors are the same as the upstream sensors
One air charge sensor held by a torx screw and one air temperature sensor with a fitting as previously described
Grease the o-rings to make fitment and later removal easy

To release the locking mechanism on the sensor plugs, push the white clip back with a screwdriver, then with your thumb press it while you pull the connector free

If you have already cleaned the sensors before the throttle body, there is still one sensor downstream of the air filter and before the turbo
Unclip the connector and turn it a quarter turn anticlockwise and lift it out

The diagram shows the position of all five sensors for sensing temperature and airflow