[Gaz64]

Rune,

Run the smallest needle and seat that still gives maximum power.

You can get 1.75mm up to 2.5mm in 1/4mm steps.

If you are on an oval and only turning right, it may explain your richness on the left bank.

You may need to machine up some spacers to emulate a canted intake manifold, with the carbs leaning towards each other.

The main well and the discharge nozzle are line with the centre of the float bowl volume, and it would be difficult to overcome your problem any other way.

The float hinges from one side and will have more closing force on the valve with the fuel stacking up on the other side of the carb, thus giving a lower "fuel level" at the nozzle. The reverse is true for the other bank, thus one bank rich, one bank lean.