TJ,
The wire leaving the ECU to the O2 sensor is coaxial . A center conductor
with a grounded shield.  If the two meet, symptoms similar to yours develop.
It will run fin until operating temperature is obtained and the brain
switches to closed loop, where it sees a ground. A ground equates to lean
mixture which the ECU tries to correct.
Since the previous owner butchered the wire in exactly this spot, I would
start looking there.
Good Luck
Ken Lewis
http://neksiwel.20m.com/