Big Block Tunnel Ram 660s Questions

Maybe I need to video what I am seeing.
That's not a bad idea. A data logger would be better and it will show you a lot more than you would think possible.

Stab throttle from a rolling drive to WOT, it falls on its face, then recovers and pulls until I lift. Stab to 3/4 throttle and doesn't stumble at all. This seems like accelerator pump shot.
Here's a hint: The fuel from the Transfer Slot reacts much quicker to throttle movement than the pump shot.