Has the ECM ever been rebuilt? When mine went out on my '90 about 5 years ago, it was running perfectly till it cut out as I slowed for a stop light. It cranked but wouldn't catch so I had to push it out of traffic. After sitting for about 15 minutes, it did start and I was able to limp it home at about 25 mph tops with some bucking. Drove about 8 miles and it died in my driveway! Swapped the ECM from what was then my project '91 and it ran fine. I had the ECM rebuilt for about $200 by an outfit in FL and re-installed it and it's been running great ever since.