holley carb help,transition/stage

should I look at also changing the iab in the rear

progressive linkage
Bringing the engine to 2000 rpm in staging even with an automatic I doubt the linkage has moved the secondary throttles open at all.
If you want to test the effect, make it seperate test. It may impact what happens as you leave the line. I haven't experimented with that myself so can't offer a first hand perspective on it.