Oh the dilemma.
I have successfully used Bosch Platinum + 4 plugs in some applications, but have not tried them on my Mercedes.
For my car ( 2000 C230 K ), Bosch lists a +4 plug, but I decided to stay with the F7 KTCR, as called for in the manual.
You can not adjust the gap of an +4 plug ( says so right on the box ).
Even though the +4's have 4 ground electrodes, they still have just one fine wire centre electrode.
To each his own, I guess.

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2007 C 230 Sport.