High rev problem

[stratosTRD]

Problem found and solved.
First of all i found out that this wire goes to the circuit open relay as shown in the pic. Luckily i didnt destroy it.


But first things first. I've installed a 20v blacktop to my ae86. I've removed the plenum and use itb's. So the idle tube of the idle control valve is tapped with a screw.

Now with a 100% rare coincidence when i turned off the switch of the cable i told you, that screw might have been loose and with the engine vibration when it was dying it fell to the floor. Almost immediately when i turned off the switch. So the idle tube sucked air freely and caused the high rpm.
The fact now that these two events happened at the same time made me think that the high rpm was because i turned off the switch under load.

Anyway i found the screw and put it back in the idle tube more secured this time. And the problem was fixed.

There is only one mysterious thing to be solved now to my curiosity, because i dont now about electrical circuits.

With the screw in the idle tube, and if i have the switch at the OFF position(as if for example the black wire would be cut), the engine wont start. If i turn the switch ON it starts normally.
Now when the idle tube is not tapped( these were the last two days until i solve the problem) the engine fires up even if the switch is OFF(as if the wire was cut permanently), immediately at 2000rpm as i told you before.

Now can anybody more familiar explain me this weird thing?
What could possibly be the connection between the relay, the idle control valve and the idle tube being tapped or not!!!