guess: calibration of tps at idle, (possibly part throttle?), wfo.
IF the tps communicates with the CDI, and the CDI controls the (rate of) ignition advance curve...
it would seem that the system is based solely on ignition advance.
after start-up, if the idle RPM speed is too low, the system advances the timing to raise RPM.
(if RPM is too high, retards (hahaha) the timing).
at wfo, there may be a either a set maximum value for timing advance or it keeps adjusting the timing
until a maximum set RPM value is reached.
whatever the case, calibration is necessary to determine tps min and max values, or the
motor advance would be out of sync with RPM?
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another possibility, would be that the tps gizmo also houses an idle air control motor, (IAC).
the IAC motor would then control the butterfly opening. this would add complexity, and cost.
so, maybe this is not the case.