Wire Shielding EMI or RF Noise?

[Bobby Fazio]

I am still having issues with erratic tach signal at high rpm in the data log and I even see it on the tach as well. My data logs have always been very choppy and jagged which makes the ECU do crazy things and even hits rev limiter which I have set very high.

I shielded my trigger wire that goes from ECU to Crane ignition box. I make sure to keep Magnecor wires away from sensor wires. Some distributor power and trigger wires DO pass by the alternator which makes me wonder if that is an issue. I have checked all grounds, made new grounds, use dielectric grease on plugs and boots, not sure what else to do.

I am told it could just be the nature of a dual-sync distributor that gets its crank signal using the hall effect and harmonics involved but I would like to know which other wires may need shielding.