Gibson's got the right idea here; if moving the COP moves the problem, then you can be virtually certain it's the COP. I'm not sure I understood your previous post, did you get 8 new COPs for the tuneup? If so, I would suspect that the new one isn't bad and that something else is causing the misfire. It could be a wiring problem (including the connector) or perhaps a PCM problem. It could also be fuel; an injector. But in spite of all this, it sounds like the folks you have working on it are doing the right thing trying to narrow it down.

I know it can be discouraging, but it will get resolved. Then look at it this way, you'll have this wonder experience you can share with someone else who comes here seeking advice.