[2.7RACER]

GotaT,
The idle air correction screws reflect the air flow around and past the butterfly's of each individual throat.

The more air flowing past a closed butterfly, the less air required to flow through the idle air passage.

Remove the carbs and look through the bottoms against a light.

Note how one or two butterfly's pass more light.

Those same butterfly's pass more air at idle and require less air to pass through the idle air screws.

To properly fix this requires re-seating the butterfly in the bore of the carburetor or adjusting the butterfly shaft connecting collar between the bores.

Once all three of the butterfly's are properly seated and closed the air flow past each butterfly will be similar to the adjacent bores.

If the air flow is the same or nearly so, the idle air correction jets will end up being set close to each other.

Differences then will reflect the individual cylinder air draw.

Regarding the idle fuel screws in from 1-1/2 turns indicates idle jets that are too large.

Go down .05 mm from what is in now. That is if you are running 55mm idles, go to 50mm idles.

This will also help the rich condition at 2500/3000 rpm.

Popping in the exhaust indicates rich, popping in the carbs is lean.