If you google this it is likely EMI AKA RFI (radio frequency interference.) The high output power going through the plug wires can actually trigger the MSD. Do a search and make sure your new wires are compatible with MSD. Then, check the routing of the plug wires close to other, low voltage and trigger wires, like, the trigger from your dist feeding the MSD. Make sure the trigger and other sensitive wiring is run close to the firewall or other body metal "ground plane", keep the plug and coil wires away from them, and cross them at near right angles. Do not run plug wiring parallel to sensitive trigger/ sensor wiring.
This type of deal has developed into a whole science due to EFI, sensors, triggering circuits, and other very low power circuits next to high power magnetic fields
