On Friday, February 3, 2017 at 3:25:05 AM UTC-8, wrote:
."The problem is that anything to do with the emission control system has to
be certified to not alter the emissions of the car. ...

Many 30 year old cars had computers. They were basic, just controlled fuel mixture and ignition timing.

I've got a computer in a car that old, and it's NOT basic, there's a bunch of
solenoid drivers for vacuum control valves... or thermactors, or somesuch.

The microprocessor is of the MCS-96 family, the whole line of which was obsoleted
by Intel a decade ago.