Starter not disengaging?

After further diagnostics there "IS" power remaining when the key springs back into the run position. I talked to Painless Wiring and they recommend a diode be installed in the circuit. We agreed the diode needs to be inline on the wire that runs between the Ignition post on the starter relay and the ballast resistor. We believe power is being back fed from the coil to the relay which powers to solenoid after the switch returns to the run position. I'm installing the diode tonight. We'll see?
If power is coming from the coil IT IS NOT WIRED CORRECTLY and you don't need a diode