You could also not be getting an even dispersal of the water/air stream.
By this I mean the intake ports closest to the TB / Intake get the majority of the flow and the banks furthur away are still heated. The problem with water cooling is it still does not address the heat in the intake manifold. Water/air cooling can only address the heat of the incoming air.
To prove this, put a thermal probe on your intake manifold at different points. If you have a temperature shift greater than 30F from one point to another you may need to address the problem somehow. IE: 160F at the rear of the intake and 190F at the front.
Here is a link to the thermal probes I use. At $20 it is a real bargain. I leave mine installed in the engine bay.
http://www.directron.com/driverrack.html Yeah it's designed for PC's, but I have had no problems.