Car runs fine up to about 1500 RPM. It also runs fine above about 2200 RPM.
Between 1500 and 2200 RPM, the tach shows half of the actual RPM, and number 1 and 4 stop firing all together. I discovered this using a timing light with RPM readout. I was checking the rpm of the tach against the timing light. When the RPM hits 1500 and the tach goest to 750, the timing light stopped firing if it was on number 1. Move the timing light pickup to number 3 and it reads the correct RPM.

So I checked it with an oscilloscope on the primary of the spark coil. The ignition pulses are evenly spaced and identical (without noise) as the engine RPM climbs to 1500. At 1500, the time between ignition pulses doubles as number 1 and 4 stop firing. There is no hint of any signal trying to fire 1 and 4. When the RPM increases to 2200 or so, the ignition pulses start coming twice as fast as number 1 and 4 start firing again.

I changed the cranksensor.... no difference

Don't think it can be the power amplifier. The power amplifier doesn't know the difference between 1 and 3.

Possibly something in the Ignition control box, but it seems so controlled...it's almost like it thinks it has to try to impose a rev limit.

Could it be a bad magnet or whatever on one side of the flywheel... but if so, why does it work above 2200 and below 1500 as well, but not in between?

I'm out of ideas.

Richard