On checking my original plug leads on my 1968/69 911E I found them to read different on my multimeter 2 read 1k ohms the other 4 read open circuit, being copper wire type ( Beru ) I would not expect open circuit, I took the plug caps to pieces and found inside a 1k ohm wire wound resistor which was open circuit I replaced the resistor with a wire link, I did this to all 6 plug caps, this should make the leads problem fee ?,
I took the car for a test run OK.