I have a theory about the Id and Ego... I don't know about the Super-Ego or Super-Id yet.
I think that perhaps in Socionics, the Id is actually part of a type's motivations, but it's not the part that's consciously acknowledged or thought about. People tend to deny their Id in favor of their Ego, because the Ego relates to their sense of identity. When they listen to their Id, they're operating on instinct, on an unconscious level.
Using Ego functions usually does feed the Id functions to some degree, but without having to engage them directly or consciously, which allows the person to experience more psychologcal comfort than they normally would.
It's even possible that the Id functions are STRONGER than the Ego functions, but they have to be repressed, because they operate in a very instinctive fashion that cannot be molded to be socially appropriate, or permit a sense of personal identity. The way these functions would be used, also, would differ greatly from how they would be used as Ego functions... the manner would be more spontaneous and less conscious/clear.
Does that make sense?