That is why people love/hate it. Using just TPS and rpm is termed "alpha-N" control. It is a rough way to infer inlet air flow (to set fuel injector flow) and is mainly used by race cars that don't have a good Pman vacuum signal. The O2 sensor corrects in the end, but the computer seems to give it limited authority, so you can get out of range. When the O2 LED flickers, you know it is controlling by O2 feedback, but your 2D box doesn't have an LED.
I found good info on O2 sensors on some site, probably Megasquirt. There are 3 wiring systems for classic "narrow-band" sensors - 1 wire, 3 wire, and 4 wire. 1-wire and 3-wire use the exhaust pipe as sig-, while 4-wire uses a dedicated sig- wire. 3-wire and 4-wire have 2 wires for a heating element to get the sensor to operating temperature faster. The earliest ones (my 82 Aries) were 1-wire. There is a standard color code for all. All have the same thread. Mainly just connectors vary. You can find "universal" ones on ebay where you cut the old connector off your old sensor and butt-crimp to the new one. Wide-band O2 sensors usually have 5 wires and the Bosch connector is most common. I think running sig- thru the exhaust pipe is fine since it has worked for years, though a dedicated wire is always better.
