hey, was searching the site and I have the same problem as you do http://www.toyotagtturbo.com/forums/showthread.php?101777-Oil-light-cut-out&highlight=idle
I also experience the exact same as you have explained. Normal Idle around 900 and when coming to a stop at a light goes down really low, and cuts out sometime. I was under the impression that my ICV might be knackered. Were you able to diagnose what exactly the cause was?
I have not hosed down my engine bay, but we did have very heavy showers recently, so could be similar causes.
Does your engine cut off when you unplug the ICV?
I also experience the exact same as you have explained. Normal Idle around 900 and when coming to a stop at a light goes down really low, and cuts out sometime. I was under the impression that my ICV might be knackered. Were you able to diagnose what exactly the cause was?
I have not hosed down my engine bay, but we did have very heavy showers recently, so could be similar causes.
Does your engine cut off when you unplug the ICV?