I am suprised to hear about cutting the wire.
I have also another solution.
( I think the better solution because cutting wires is not a Alfa solution )
First what i replaced:
1e The Lambda sensor
2e The idle speed motor
Nothing helpt so far
I connect the pc with Alfa diag and go to the actuators and let the ecu learn
the new idle speed motor.
Also that was not the solution.
After a lot off thinking i notice that most people have this problem after 150.000 - 200.000 Km.
The solution is easy.
Turn the screw on the gasket ( to adjust the air intake valve )
about 45 to 180 degrees.
After turning the screw ( see photo )nothing changed , but when you connent the alfa diag and learn the ecu the new mechanical position of the valve everthing is perfect.
If you turn the screw let say 360 degrees and do the alfa diag you going to see that he idle speed is to high.
After a while the idle speed wil go down to 800 rpm.
You must do turn the screw by traile and error.
Starting with 180 degree is a good starting point.
Now the reason why i did the screw.
When you watching the screw you can see that the screw is a little bit shorter if you compare it when the screw was new.
By turning the screw you put the valve again in the old position.
ONLY TURNING THE SCREW DOES NOT HELP.
Always after turning the screw connect the pc.
If you questions you can always email me.
( I hope that everbody understand me verry bad englisch story )