I've found the M103's are more sensative to ignition bits being in tip top shape then 117's/116's, 110's etc.. Usually by around 30-35K the rotor on my wagon was showing it's age (wear beyond what a good clean would tend to).

A note on the Bosch plugs, they will no longer be manufacturing the non reistor type plugs, so you'll want to stick w/ NGK or I've heard the Beru plugs are decent as well.

For an M117 I like to run W9DC's gapped a 42...

Jonathan

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