That is pretty interesting. Two questions come to mind:

1) if the injection pump acts as a filter, then should not you need to clean it out once in a while? Not done on my 81 300SD ever.

2) I have changed the in line filter - should be clear- but have never changed the one in the fuel tank since 1981. Have never had a problem. Does MB recommend that this one be changed on any periodic basis?

Thx