Instead of pulling the O2's, there are a couple easy voltage tests you can do on them to see if they are working correctly. If you don't have a copy of the book "Ford Fuel Injection & Electronic Engine Control", by Charles Probst, I'd deffinitely pick one up. It covers how to test nearly all sensors on your motor. It's the best money I've spent, and has more than paid for itself by letting me avoid replacing perfectly good sensors I thought were bad.
There may be a newer version of the book out.
I still think that you and I are in the same boat with the problems we're having. I'm beginning to think it's more of a timing issue - not enough/no advance. This could create a temporary rich condition when you're reving it. It also would be a problem that could come on suddenly.
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