I was thinking the same thing! I believe the "R" in "TR5" refers to resistor, and you want to stay away from them in this older, lower output ignition system. With resistors in the end caps on the ignition wires, and possibly elsewhere - read about one being in the rotor and in each distributor cap terminal - you don't need to introduce another in the circuit. Mercedes does not recommend plugs with resistors because resistors are already in the system. In addition, Mercedes does not recommend platinum plugs because the resistance of platinum is higher than that of copper and along with the resistor found in platinum plugs may provide a weaker spark - especially at higher RPMs. In our older cars, the coil is probably putting out between 40-45,000 volts max., compared with up to 80,000 volts in high energy ignition systems found on slightly newer cars.