750 Edelbrock issue

I bought a new 750 edelbrock a couple years ago. I bought the strip kit and did all the tuning on a mild 383 with an air/fuel meter. No matter what i did i could not get rid of an off idle dead spot. I mean DEAD, if you held the throttle right off idle it would die every time. I tried everything, something is just wrong with the carb. I restricted the idle air bleeds, drilled the idle fuel restriction a little, adjusted the mix screws to perfection, fattened up the accelerator pump shot, all of which helped a little- but it still does it. Ive worked on carbs for 30 years, never seen anything like it.

The idle, cold starting, hot starting, highway cruising, WFO, all work great- the car got the best miliage ever.... but that dead spot will not go away.

Switched to an old 9000 series carter and it works great.