I should have been clearer regarding the tach sensor.  My aircraft has a G900X and Slick 6320 pressurized mags.  Installing the G900X involved removing one mag's pressure vent plug and replacing it with a UMA T1A9-1 tach mag pickup.  This particular UMA sensor is really not supposed to be used on pressurized mags because it doesn't have a vent hole;  and sure enough it led to moisture buildup in one of my plane's mags (350 hours).

The person at Aircraft Magneto Service told me the spark plug resistor isn't there so much for RFI suppression as it is for current limiting and shaping.  He said the ignition harness acts as a capacitor, and the harness + resistor + spark plug form an RC network and thus affect the shape of the current pulse(s) inside the magneto.  He said removing the resistor not only leads to rapid spark plug wear, but also stresses the magneto and associated components.  At least that's what I think he was telling me.....

I have no intention of substituting a 0 ohm resistor in the spark plug....i was just wondering if any of our Reno racers really do it and see any difference.