[Gaz64]

The 120 holder is giving you lean progression.

Start small on both, get it to idle at 3/4 turn out on the screws, then open the throttle with the speed screw to check progression.

If the 100 holder can't richen progression, even with a 65 or 70 idle jet, you'll need the third progression hole drilled.

This is more common with 48 IDAs on a little engine. Makes driveability a concern for a street car.