[Kenth]

The idle/low speed circuit is a separate circuit independent of the main jetting.
If the main jetting were to affect the idle/low speed circuit, the engine would not run at all.
So it doesn't help to change the main jetting to lean out the idle/low speed mixture.
Then smaller idle tubes or/and larger idle air bleeds must be used.
To reduce the amount of this mixture down to the lower idle air bleeds and mixture screw tips, smaller idle channels must be used.

For your 1971 Pontiac Qjet carburetor with the primary pull-over system, I would use correct style primary rods (without the B suffix) stamped 73. (EDL-1944).
The adjustable main airbleed under the triangular retainer seated to start with.
For the idle/low speed circuit, I would start with .038"-.040" idle tubes and .057" idle channels for a 455 w/RAIV cam.

To check if your efforts are close to optimum use the "tip-in" test at idle speed an at 2200 rpms. If good and no hesitation while driving you´re fine.

FWIW