Found this odd harness under the dash. Looks like old alarm wires but there's a large plug that's plugged into nothing...

I'd post a pic but I'm on the mobile site. I'll update with a photo short.

 

maybe OBD socket?

 

Well without pics its impossible to tell. But it could be one of three things off the top of my head.

1. OBDII port
2. Factory Alarm Harness (it was an option on some cars, i have it on mine. look for a red led installed somewhere to indicate you have the alarm)
3. Aftermarket alarm that was removed and they left the harness