We have discussed this here before, but the reason for different jetting was that the central two cylinders fire on alternate complete revolutions, whereas the outer two pairs are not evenly spread so one cylinder starts inducting before the other one has finished. There is a danger of a leaner condition due to the more intermittent nature of the air-flow, so slightly richer jet settings are used, e.g. 5 points up on the main and/or 5 or 10 points down on the air corrector. I have no idea why the emulsion tubes would be different. I suspect that any differences in emulsion tube are due to later experimentation, rather than a factory setting.
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