Hi, i was learning about mixture and idle calibration of my FC non turbo 1986 on youtube and i just figured out that my car has no air pressure sensor, and no o2 sensor either, don't know if anything else is missing. I know that the last owner changed the exhaust, the suspension, the mass air flow meter and the fuel pump, i don't know yet what exactly he changed in the exhaust system even if it's connected to the egr and ports 5th and 6th, im trying to undo the modifications of the exhaust so i'll thank you if you could explain me how and why could my car run without those parts and if i need to reinstall them. The car works fine, i can't notice any problems with idle or anything else, just that the exhaust is extremely noisy.
Here are some pics, please tell me if you see something weird.
Thanks!

There should be the o2 sensor i think.


Some connectors unplugged.

General view of driver side.

There should be the air pressure sensor.

General view of passenger side.