Perhaps this will help someone out...

For months I experienced engine stutter when accelerating or under load. Felt like engine is running out of fuel. I first replaced the fuel pump, filter and since that didn't help tried with all sorts of jet/rod combos, different carb power piston springs...with some limited effect. Than I turned to ignition, since the symptom was also similar to ignition miss under load.
Changed spark plugs, tried different gaps, new cables, rotor&cap, module,....all but the HEI itself. Nothing helped. Idle was fine, so was cruise, although the vacuum gauge did show 1/2 inch rapid vibration at idle.

All that until I replaced the HEI distributor itself. Looks like either the magnet pole or reluctor coil can make it feel like fuel starvation at WOT...or light but annoying miss under load. It check's out OK with the ohm meter and it was new when installed...

 

I'm assuming the hei straightened out your issue.

 

The coil and the magnet was the only thing left to replace...but it was easier to put in another distributor. I assembled one from different parts I have, to make one used "Frankenstein" HEI distributor...just too see if it will make any difference. And it did. Since the magnet and the coil are only parts of the distributor that ware not replaced before I assume one of them created the problem . It runs like a dream now!

 

The old addax that most carb problems are actually ignition issues still holds true.