Camelot,
After going through the same exercise as you, I think that I now a
slightly better understanding!
MB wanted all wires to have the same resistance and at same time prevent interference with the radio and electronic engine components.
What they did, was use a very low resistance wire (stranded copper), and then they added a resistor at each end in the caps. My old wires measure 8kohms from end to end, the two reisistors are 1.6 and 6 kohms for 7.6 total, so wire is about 0.4 kohms for total of 8 kohms. (Using my old multimeter).
If new Bosch spiral wound wires are used, the wires them selves will have a resistance. I measured mine at 1.6 kohms end to end. If non-resistor plugs are used, this would mean your total resistance would be 1.6 kohms and it would change with length - Difference could be as much as 20%. If you use resistor plugs with say 5kohms resistance, then the affect of the differing wire lengths would only be about 5%. So, it seems to me that it would be advisable to use resistor plugs with wires that do not have built in resistors.
BUT, to add to the confusion, Bosch say this on their site:
Not with Bosch Premium Wire Sets. Electromagnetic interference (EMI), also called radio frequency interference (RFI) is caused whenever a current flows through a wire. This current creates a magnetic field that can disrupt other sensitive electronic components such as the engines electronic control unit or radio. For Japanese and domestic applications, Bosch wire sets have a RFI absorbent shielding material to eliminate interference. In European applications, a solid copper core wire is used with OEM-style resistor connectors that absorb unwanted EMI.
The Bosch Premium Wire Set box says it is for MB V-8 engine, but the wires do not appear to have built in resistors and a resistance check confirms this.
I called Bosch, but just got the run around - the guy was not knowledgeable and just wanted to get me off the phone. Bosch Canada did not respond!
It would be nice to put this subject to bed. But without cooperation from Bosch, that won't happen!
I wish I had bought the Beru wires.
Their website provides extensive info on their wires and plugs:
For example:
http://www.beru.com/download/produkte/endverbraucher_zt_e.pdf