I live in South America so the version of my car, a D16a9 Civic SI sedan, came OBD 1 with no Catalytic converter. So, wtf? Does that mean it has an O2 Sensor without a CV? Or does it have no O2 Sensor?

It has after market headers with no O2 sesnor.

I'm so confused.

 

OBD-1 is a diagnostic system... NOT an emissions system. I cannot tell you for sure whether your model came with or without a CAT, but I can tell you that your Primary O2 sensor has absolutely nothing to do with the CAT. The O2 sensor is for maximizing fuel efficiency for idle and light throttle operation. Is your car fuel injected ?

OBD-1 means OnBoard Diagnostic System - Generation 1. This is simply a list of standardized diagnostic/troubleshooting codes along with an ECU subroutine that detects sensor presence and sensor values that are within/outside specific voltage or resistance ranges to help diagnose and repair engine function.