If idle is high, it is getting too much air.

Find out why or where.

When it is idling too high, is the ecu trying to reduce the idle ? ie what sort of signal are you getting at the ISCV ? if any ?

Is the throttle blade where it is supposed to be in the "closed" position ? again, check TPS voltage as per specs on the website or a manual.

You do not try and alter fuel mixtures by messing with any screws on the throttle. You need to adjust the mixture screw on the ecu.

Fix idle speed first to a sensible level.

Then adjust mixtures the correct way.

And what sort of ignition timing is it running at idle ?