hitting boost ceiling w/ WI?

[GTTechnics]

I currently own a centrifugally supercharged VR6 (VW) running 9psi of boost and 10:1 compression. I am preparing to change the pulley size to the smallest available (15psi). Due to space constrictions, a water/air intercooler is somewhat impractical, so WI seems like a good option. The company supplying the pulley offers fueling and compression kits (lowering to 9:1, 8.5:1, or 8:1). They claim that the 15psi pulley is safe to use with their fueling and the 8:5 to 1 spacer. On a side note I live in the desert (Arizona).

Assuming that the kit is safe, I have no control over ignition (other than what the CPU gives), I can't further increase the boost, and I can only tweak air/fuel ratios (straying from the above fueling kit) with an adj. FPR....how effective will water injection be for me? As far as I understand I will probably regain timing (and therefore low end torque),and be able to lean out my air/fuel to a more reasonable ratio (as well as provide more consistent performance on hot days and give a margin of safety).
Am I correct? Is there anything I have missed?

[Richard L]

I think we need to work backwards on your application.

Do you experience power losses in your region due to dry air (more prone to knock) and high inlet temperatures?

If the answers are yes,yes. Then WI will help a great deal. Due to the dry air, water evaporation is far greater.