Timing problem

Look at the tiny vertical slots near the blades in the lower secondary throats; those are are the secondary transition circuit slots. The typical adjustment of that screw would be so that the portion of those secondary transition slots below the blades look like squares when the blades are closed. In other words, a bit of each slot should appear below the blade when closed. You may have to adjust it again from there as you get the car running and test it out.

At idle, this secondary adjustment will effect the air flow into the engine, and thus will effect where the primary blades want to sit at idle. The primaries at idle should also sit so that the just the lower end of the primary transition slots are exposed under the primary blades. If the secondary blades are too open or closed, it will effect the primary blade setting and that in turn effects primary transition circuit operation, and that is how you can get the slight off-idle bog.

The t-port sync is the combination of the 2 transition slots openings.

Here is a pretty good discussion:
Holley Carburetor: Idle and Transition Circuit Calibration Guide