Ok,

That cylinder that the injector bolts into is the pre-chamber. If all of the threads came out and all that is left is the end, you should be able to take out the injector and the prechamber and clean the prechamber. There is a special tool for reaming this out with everything installed.

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Benzmac:
Donnie Drummonds
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS