The original platinum spark plugs are the model F8DPER, single pole with a
of 1380 Ohms. The newly recommended replacement from Bosch USA is the
Platinum + 4 pole 4418.
Interestingly, measuring the resistance, not showing any continuity
between the center electrode and rear connector pole.
The BOSH USA tech support is not helpful with technical questions.
It looks like the center electrode has an internal secondary gap.
The recommendation from a Mercedes mechanic with years of
experience is, that I should not use the 4-pole platinum sparkplugs; it
will cause spurious engine problems.
A mechanic, member of the Mercedes racecar teams, told me that they using
NGK spark plugs.