Always use a resistor spark plug if available for your engine. Even if your ignition is a full shielded system.The CM-6 is a non resistor plug so we use a resistor in the spark plug cap. I have gave up on resistor spark plug wire .The old Beldon resistor wire was good and we used it for years,then Beldon quite making there own wire and problems started. I see RCEXL has quit the resistor wire and uses a resistor the the cap for the 10MM spark plug CM-6.
We have a RF meter that will tell you right now if you have RFI. You should see what a Fuji Ign does to our meter.
I built a very noise ign system to check out the 2.4 radios.With a resistor spark plug my range checks were fine. Put in a non resistor plug and it ate up the 2.4 system both the FASST and the Spectrum.This was good enough check for me. ALWAYS USE A RESISTOR SPARK PLUG.................
BCCHI