Trying to track down a high rpm missfire, I noticed that the RPM jumps, say from 5800 to 5400 and back, when the misfire occurs. I can't imagine the engine speed is actually changing that rapidly, so I thought I'd ask to see if this is a clue to anyone as to the cause.

It's worse when hot, worse under boost, worse with a larger plug gap, and I've tried with and without the CraneHI6 and PS92 coil, no different.

I know everyone wants to say opti, but I'm hoping there's an easier solution...

 

If you are having a true misfire and not just saying that because of the tach. Chances are good the opti is on it's way out. The PCM uses one of the feedback signals from the opti to drive the tach. Since both firing the plugs and providing feedback for the tach have a common point at the opti, there's your sign.