You got me a little fckered on the OBD1/2..
OBD1 has one.. (pre-cat)
OBD2 has two.. (pre-cat/post-cat)
If you have two connectors for 02 sensors.. and one isnt connected.. like a pre-cat/post-cat
Or if you have the wrong 02 sensor plugged into the wrong spot..
I dont know the specifics of your swap.. but I'd like to think something is just being overlooked..