The ECUs go bad with age, electronics and leaking capacitors that are not designed to last, its their nature as they are filled with a liquid. Chips will go bad to. And being left outside in a car over time and many different weather conditions wont help electronics. The Supra community needs someone who can actually do electronic repairs with garuntee, theres a few on social media who have the gift of the gab and nothing but bad reviews. I myself spoke to them and they just seemed to want the parts and payment with a whole load of chat.
Someone out there must be able to make the boards of a early 90s Toyota ECU