a Friend had a supercharged 454 (1990) that the cam was off 3 teeth it would show in time with the efi but it ran eye watering rich, had to tear back into it, correct cam, efi acted perfect after that.
I think the efi was hunting for the right signal/nixture. I cant believe it ran as good as it did.

Keep us posted what you find out.

Godspeed
MrC.