The website has the basic setup and information a half decent technician would need, as will the manual I linked to with a more guided approach.

So you're saying the car has sat and not moved or been used for 20 years ?

So it did not run correctly 20 years ago when it was "stage 1", but now somehow it is "stage 2" ?

Would you not be better to fix the car first, before messing with the ecu ?

If it is idling too high, then the engine is getting too much air. If it is too rich, it is also getting too much fuel.

If it has sat for 20 years, it absolutely will need the tank drained of all fuel, new fuel filled up, new filter etc etc. Injectors may also need tested and either cleaned or replaced as necessary.
Check the fuel pressure regulator is working correctly, and not failed and chucking fuel in via a ruptured diaphragm into the inlet manifold via the reference pipe.