Need some help identifying sensor

When I replaced my head (0331)on my 2000 I left the sensor (under the coil rail/above the oil filter) at the machine shop. Anyway the new one is the same casting but w/o the sensor the electrical connector is just hanging there so im trying to figure out what the sensor was for. Can't seem to find it in the FSM. Any help would be appreciated, thanks.

oil pressure sending unit?

just one wire?flat connector?

Yes it was connected to a flat piece of metal that was bolted near the bottom of the head.

knock sensor?

Edit, nevermind, I didnt see it was a 2000