As long as the Throttle plate is closing down ass the way, the base idle adjustment is not opened up from the minimum.I would then consider the isc
The isc is not driven or related to the caps,
I used to know this circuit but it has been a long time since soldering part inside an ECU.
The row of dual relays has or had something to do with idle but mostly control thing like fuel pump and other devices.
Not having these fresh in mind and with the dumming down online searches to paid advertisers only I am not really sure how to assist.
I will try to get this back in my mind since 15 years ago I have been there.