Given your response, I would be looking for a wire with a defect (cracked insulation, broken internal core, etc.) or possibly your movement placed an ignition wire in direct contact with another, sensitive wire that is feeding the noise into your avionics. The ignition wires do get a magnetic field around them that builds and collapses. The collapsing magnetic field is energy and can be absorbed by another wire that it too close. Not sure this is technically RF, but it will appear and disappear with each spark event (i.e. tied to the RPM).
The EGT is a VERY low current signal and could be influence by this type of magnetic field. Look for areas where you have long, parallel contact between an ignition lead and EGT wire
In summary, you should be less worried about the wires touching each other and more worried about them touching other sensitive wires. I have EI ignition wires that are tie wrapped together for 2-3' and have no interference.
Larry