That's a matter readily solved by a PID controller made of a few dozen 74XXX parts. Possibly made n-times redundant.
Even a more fancy LP solver probably wouldn't need a fully fledged computer.
I mean, I could implement a PID controller without any 74xxx logic at all: a basic op-amp, a handful of resistors and capacitors and boom I'm done!
But there's a reason that engineering doesn't do that these days and it's not that engineers don't know how. My PID control built from an opamp? In 2021 that's almost always a stupid idea. We use computers because doing it digitally has many advantages. We don't use 74xx (or any other logic family) for this because microcontrollers are far more flexible, allow for behavior changes without reworking hardware, allow inventories to scale (the same component can be used in hundreds of products) and more reasons I won't detail.
The reality is that in 2021, often the simplest, most robust and cost-effective way to do something trivial is by using a computer to do it.
Very much not. Complicated MCUs are a very risky single vendor supply, and as we see now, people are now paying for an engineering overkill.
74xxx are available in every shape, and form, from dozens of suppliers.
Repeat for manifold air temp, exhaust temp, emissions, rev limiter, etc., and as you mention, make that 3x for redundancy. Now you have hundreds to thousands of components, in a high noise, vibration, and temperature environment, and you have something which is about as efficient as an 80s car. And you can't as easily simulate it cause it's analog.
Or just use some digital chips and simulate all the tuning.
Electronic fuel injection is a _great_ example. Much of modern fuel efficiency stems from the fact that an engine can accurately control fuel in the cylinder based on a bunch of factors. Not only does this system require physically fewer materials, it uses less gas (in turn saving production effort).
What I mean under a computer is a Turing complete machine. A circuit just doing some LP solving, or PID is not necessarily a computer.
Most of the functionality of these chips can be represented in some form of hardware. However, that hardware is often much more expensive, significantly less flexible, and likely significantly bulkier.
Jadon Cammisa has a great series on this stuff. Here's just one episode on one topic, drive by wire throttle control: https://youtu.be/gKsCHx5NOMM
It's very close to what you are taught in the "How to write a PID controller" class without much extra creativity.