Kohler 20HP won't stop

I have a Simplicity CV20. My engine will not sop unless choked to death. This is not good for longevity of the engine.
I have attached new wires to the coils and then to a kill switch that goes to a good ground. When I throw the switch it sounds like one cylinder stops but the engine still runs. Is it possible the coil on the running cylinder is defective ? I also pulled 1 plug wire at a time, through the kill switch - one plug off and 1 on killed the engine BUT with the other plug disconnected and the first one plugged in the engine still runs with the kill switch thrown to off.

Sounds like the backfeed/crosstalk diode is open on the offending ignition module. Unlike Briggs the diodes are built into the module on Kohler instead of being in the wire between the modules. You can remove the blower housing and then try to ground the kill wire terminal directly to the block and see if it looses spark.