Might better to treat sub-throttle motor as boost-control solenoid. It needs to work when throttle is opened. Whereas idle control-valve only works when throttle is closed.
Sounds like good plan to switch over injectors & ignition.
Be careful with sharing sensors as that may affect output signal. Not all ECUs use high-impedance circuit for all sensors, but employ current-sensing. A second circuit will change current.
Keep up good work!
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