67 dart stroker hellcat gen3 hemi with twin turbos...

Grab a roll of aluminum foil, like Reynolds, and start wrapping wires in the harness individually and see if the problem goes away.

Just went through an RFI issue on my cousins Belvedere with RPM signal and Innovate data recorder. Eventually found where the cross-talk was happening, then insulated the problematic wires and all is good.