DSMs of that time period were notorious for capacitor failures inside the ECU. Get someone who knows about DSMs to take a look inside the ECU for you, and test a few things if they know what they're looking for. If I remember correctly, some say the caps can be replaced and the ECU will work fine, other people say it will destroy the ECU. I don't know for sure, I just remember hearing about this during my ECU hacking travels.

Google to the rescue: http://www.90gsx.com/eclipse/cap/caps.htm