Very nice clean setup you have there.
What I have found is that on the mappable system if your duty cycle is low then you wont be spraying enough water.
At what point are you triggering the water to come on I would reduce the trigger point and test the temp again or go with a larger nozzle.
The water is there to reduce the intake temp and prevent detonation if its not doing that you are not spraying enough water.
There is another board member that did a test and got very small drop he went to a larger nozzle and got 70'F drop in temp.
http://waterinjection.info/phpBB2/viewtopic.php?t=25
Go to a larger nozzle you will know when you have too mcuh water the motor will bog down and not pull as hard and sharp.
In the summer I use the 1.0mm and in the winter I dont really drive the car but go down to .7mm-.8mm