Where is the 02 sensor box for 1991 dodge with Mitsubishi engine?

No such thing as a O2 Sensor Box. The O2 sensor is located somewhere on the exhaust system. Looks similar to a spark plug with a wire connected. May be more than one. The o2 sensor on my 1990 Mitsubishi Mirage 1.5L (same engine as the colt i believe) is on the exhaust between the manifold and the catalytic converter