Warp,
No one has tapped any fittings. This subject came up because of a running production change in one of the plastic fuel lines - originally it was a push fit O ring, but it got changed to a banjo with a hollow bolt. The hole in the IP is already threaded to receive the bolt. Surprising but true. If you search this subject you'll find diagrams, etc.

Rgds,
Chris W.
'95 E300D