I have an issue with my idle speed that I believe is related to the signal the ISCV is recieving rather than the valve being faulty, with the valve being disconnected and the car heated up it idles as normal, with the plug connected to the valve it idles between 1500-2000 rpm, so that would say to me that it is being "told" to do this, when in fact it doesn't need to, so my question is, what governs the operation of the valve?

I see from the diagrams that it has the common black/red wire or positive +12V supply and then another wire wich apperars to be connected to the TPS, like a swithed earth or signal, i think this is where the problem is, but cant really go any further than this.