As ignition spark plug wires get old, do they emit RFI? If they were rated 50 Ohms per foot, whats the acceptable threshold limit as they age? The wires are working, no driveability or performance problem. They're just picking up RFI noise in radio & same car on chassis dyno that used to read RPM signal fine. Now it disturbs RPM signal to dyno electronics gets interference, where unable to read with inductive pickup hooked up due to what I mentioned. Thanks in advance.