The point of an intake sensor on the e36 325i is to tell the DME (computer) how dense the air going into the engine is. This allows the DME to configure the correct air fuel ratio for the car to run smooth.
If this is not connected, then I would imagine the car would struggle to identify what exact AFR it needs. Similar to the MAF sensor, which calculates how much air is going into the car, these sensors are important for the car to run correctly.
The car won't break, as effectively, your car will run in what's called Alpha N mode, where it uses throttle position and RPM to guestimate the correct amount of fuel needed. This is just a safety mode that all BMW engines have.
It will run, but not smoothly as the DME is using tables that were given to it by the programmers to get a ballpark figure of what it should do with the fueling. I stand corrected here, but from the amount of research I have been doing on Alpha N, intake temp sensors and maf sensors, I understand that the DME will run the car a little rich to ensure you do not run lean. Safety precaution.
So you may see your fuel usage go up.