carlo, firstly try setting your base idle.

run the car till hot,
unplugg the iscv
adjust your base idle (screw under throttle body) to 900-950rpm
reconnect the iscv.


then remove the iscv, and leave it soaking with thin oil in it overnight(dont use wd40) push the internal plunger a few times to clean it all up. rag it all off and refit

and try that.