It is still better to use an intercooler, howver - you do not need to go to a big front mount. We tested the same kit on our circuit car with no intercooler, and found that on the longer straights, temps were well controlled, but on tighter, on/off throttle situations, and on partial throttle where you are not using much/any boost, the water alone was not able to give a consistant inlet temp.
We have just installed a new intercooler - not huge, and already we have seen lower intake temps and higher HP figures on the dyno.
Mafia - the pic of the contol module shows you having both dials set at the same amount (approx 5psi)..... is this how you are running the system in the car? You should have the full PSI set at about 14psi in your application (assuming you are running 18psi)...this will then allow you to run a larger nozzle to add more water/meth at the top end.
Mark.