Resistor caps can fail, giving ignition problems.
Measure the resistance now and then and replace if your not at 5k any longer. The resistance is supposed to do good somehow but I don't know what kind of goodness that is. Could be to protect the cdi from damage, could be to get a better spark, could be to reduce rfi... ?
The resistor plug may perhaps be the resistance to bear enough goodness to give the blessing sought after so you may be fine with a zero Ohm cap. That is how I run it and I measured the plug to be at 3k Ohm.
Hopefully these 3k does the job and they get renewed every time the plug is changed.
Cheers