Well there's a red wire running from my positive cable through the fire wall. My only guess is ignition switch. It may not be to factory settings the PO did a lot of shoddy wiring jobs on this car.
My first guess would be "not" ignition, and part of the "shoddy" part. I would be "finding out" what it does.
Don't know if I mentioned, there's always the possibility that the ignition switch is bad..............try pulling the connector off and see if it drops the battery draw.