I have a 1990 Legacy wagon, 120,000 miles ran like a champ until about a year ago. I took it to a machanic and he replace the Ignition relay and it ran for a year and it stopped running again. I replace the ignition relay and it ran for a couple hours now it runs for a few minutes and while its running the tach bounces like a tennis ball. I am guessing that it is the ECM but I am hoping that there might be something else to try.