I will say, I have seen some real wiring idiocy....like a coil that doesn't work loading down a ballast....I have seen an extra wire to the power side of the coil...and followed it...and found it was feeding power to the fog light relays...or worse, a cooling fan relay.
Cooling fans can create some real shut down issues.
Turn the key off, and it keeps running...for a while.
Folks fight carbs, look for vacuum leaks...all because the fan motor becomes a generator when you power off, the blade acts as a flywheel, keeping the armature spinning...and you have enough power into the coil to keep it running for a while.
I got to the point I'd see how many wires were connected to the coil before doing anything else.
Dave