Now that we have the ability to modify the sounds per engine, rather than per vehicle, could you create a separate engine sound, and make it so the engine only uses that sound when the intake is changed? Similar to changing idle RPM or max RPM when a turbo/supercharger is added, couldn't you theoretically do the same for sound? Are supercharged engine sounds now possible without the devs releasing official sounds for it?
Yes, and yes. You can edit siundConfigs on a per-part basis. For example, when nitrous is activated, the engine sound increases because of a change in the soundConfig. Supercharger sounds are already ingame, though they're not implemented yet. They are possible, with some patience and engineering.