NGKs webstite says if your model has computers,which mine has them for everything,to use resistors.The noise may interfere with computer systems.
I also read a memo bulletin on m104s that said not to use fine wire spark plugs,they will foul easy.I think its because the newer engines have tighter tolerances.Where the m104s will let,or accumulate carbon,this stuff can interfere with the fine tips.I used NGK iridium and had to remove them after a 1000 miles.They kept fouling,I put regular large tip plugs in and no fouling.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran, deutschland deutschland uber alles uber alles in der welt