It gets even better.... So before I left work yesterday I tried the horn and it didn't shut down the motor. On the way home I drove by a situation I had been in the day prior. I had a fire truck coming up from behind and we were all stopped at a red light. I had honked to let the guy in front know to move over so the truck could get by. Once he moved I had to start the car again but due to the rushing I had forgotten what actually happened until yesterday.
I got home and honked while stopped and it didn't shut down, until I tried again. It did shut down a few times (but not every time) while pressing the horn in different spots didn't seem like it had "one spot" that was bad.
What I did notice was one time I pressed the horn and it didn't stall, but it did cut the ignition ever so slightly, I could see the tach blip just slightly but I guess the engine had enough rotation still it was able to "catch a spark" just enough to stay running.
I also noticed the same thing once while revving around 1800rpm but that was very quick hiccup and it was done.
So It isn't just under 1000 rpm but stalls out because low rpm looses the rotational momentum to keep running.
I also tried all the above with the cruise control on and off. Turning the wheel while using horn. All accessories off like the radio & heating. None of this seems to make any difference. I will have more time on the weekend to actually dig into it. I will need to locate a ignition wiring schematic and the horn wiring as well to see how connected they are in reality.
If I had to guess I feel the horn and the security system my be at fault but this is a completely random guess. But the thinking here is the horn is connected to the security system that is connected to the ignition for command start and stuff? Without looking at schematics it is hard to say.
If all else fails I will disconnect horn and see if it still persists, at least I would piss off neighbors sounding horn over and over to find issue.