If memory serves me, the airbox-to carb rubbers all had the same part number -as opposed to the carb-to-engine, which had to different part numbers. This means the same intake rubber is used for each one of the four carburettors, but the distance between holes in the airbox is different than the distance between carb throats. Again, if memory serves me, the two center ones went straight to the airbox, while the two outer ones were ar an angle. For that reason, the intake rubber had two different lips so you had to install the center ones with one lip and the outer ones with the other lip so they would tilt out of the airbox. As this second lip is not perpendicular to the intake rubber center of symmetry, by rotating the rubber you also modify the position of the opening, thus aligning or mis-aligning the mouth.
In any case, new rubbers and a little wd-40 applied with the finger in the inside of the rubber and in the outside of the carb mouth do help a lot.
Raul