Yup.
Excess resistance will do that.

NGK and denso still had readily available NR plugs for a Long time..europe has a better selection as well.

resistor is built into the plug. Screw on tip has no effect sadly.

jono

__________________
Blue Ridge Mercedes
Jonathan Hodgman
http://www.blueridgemb.com/
Enthusiast Service, Restoration & Tuning.
Follow Us on Facebook!
Located in the Atlanta area
Specializing in all pre and post merger AMG's including Hammers and DOHC M117 engines.
Mercedes Repair Atlanta