Hi John,
Sorry to hear you are still battleing this dragon...
I can't recall if we have already covered this but...
Have you checked the headers to make sure that the tubes are open all the way down to the collectors?
Point is, if the exhaust is blocked, you will not get flow and those cylinders that are blocked will not fire more than a couple of times before they are no longer capable of being refreshed with oxygen.
Would be a pretty odd duck to fine just one bad header tube let alone two...
You could just loosen up the headers to introduce a massive leak to run for a few moments to see if you at least have all 8 firing..
Randy, I'm sure this is not the problem.