My 92 classic just had a new engine put in. Minimal miles on it. Dropped it in and the 4th cylinder was acting like it was bad. Compression and sensors checked out okay. It turned out that the injector wasn't firing. Took it out, and it tested okay on its own. The problem was traced to the connector on the ECU. Some of the wires were bad. Replaced the connector...problem solved. Took a long time to find the source of the problem, though. Just thought I'd relate that story.

Yeah those things can be a PITA. I really don't like the place that they put the ECUS. Good to know that you found the problem though. I would have never checked there.

Believe me...tough...the original engine died in March. The car is now operational in September...lots (too much) down time.