Here is the wording from DieselGiant:

If for some reason you get a run-a-way engine, this is the quickest way to stop it. A spray paint can top fits perfectly over the turbo inlet, to instantly cut the air supply and shut the engine. Just remember to remove the air boot from the turbo to the air cleaner, before you start the engine. If you have a non turbo car, just remove the air cleaner and get a piece of wood or cookie sheet that you can put over the intake manifold opening which also will stop the car instantly. Remember an engine needs three things to run, fuel, air and heat. Take away any one of them, and it won't run.

I looked on my W126 CD1 manual that I bought (two cds) and now see where the turbo charger is. To see it you must remove the air cleaner and bracket and it is below. Is DieselGiant wanting me to use the spray can top in there somehow? Need to go out and look at the engine. Maybe talking about the ribbed black plastic hose (must be called an air boot) that fits to the front of the air cleaner - that must be an air intake. Seems like it is a lot larger than a spray can top but I need to look. If that fits, would be simple to put the top over that hole to stop the engine. May test it just for kicks.