The humming should actually be the idle air controller, it gets a modulated signal like a sign wave to keep it open at a certain percentage, an explanation of why it stops when you unplug the TPS sensor could be the voltage signal then sent to the EMS is what would be above the threshold of the EMS programming where it applies idle control dependant on throttle, I dont think the TPS can physically hum, whereas the idle air control motor DEFINITELY does, unplug the idle air controller, bet it does the same thing.....as for the noise, with the EMS and idle air controller, you arent getting rid of it, its how the ems controls how open or closed the motor is by using duty cycle to position it properly whereas with the stock pcm it may have a real fine factory tune that keeps it from having to constantly have a signal applied to it basically opening and closing it very rapidly, kind of like how you would use a duty cycle to open a nitrous selonoid only a certain amount, only a nitrous selonoid is alot louder because its slower reacting and designed different.
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