It's supposed to be dynamic. The ecu reads the various inputs ( MAF, air temp, coolant temp, knock sensor, throttle position, cam position, lamba, atmospheric pressure? and probably a couple I've neglected to mention ) and then adjusts the injector cycle and timing as appropriate.
If the car is running rich, then there has to be something wrong with one of the inputs. But, it cannot be too much of a failure or the warning light would be on.
Although to my mind it would have the effect of weakening the mixture, check the air pipes from the air filter to the throttle body for leaks and splits.
After that, eliminate individual sensors. You can take the usual approach and change components until the problem is fixed or isolate the problem. As an aircraft engineer I assume you're familiar with a multimeter? If so, checkout the workshop manual as it'll give test parameters for most of the stuff you're interested in. You'll be most interested in volume 3 or volume 3 part 2 'Electrical Diagnosis ) depending on whether you have an early or late phase one ( late phase 1s have the Bosch M2.10.4 ecu - updated from M2.10.3 at VIN ZAR91600006023907
For example, the intake air temperature sensor is an NTC thermister rated at 10K @ 25°C. Remove it and test it in the fridge, the airing cupboard and room temperatures for correct operation. Unless you fancy doing some complex maths you'll just need to satisfy yourself that it's about 10K @ 25°C and increases in resistance as it gets colder and reduces resistance as it gets warmer. Then you can use a diagnostic reader to get the heater voltage off the lambda and compare with spec etc.
Carry on until you eliminate everything and then throw the multimeter at the wall when everything checks out