Take a before and after picture of the impeller vanes. Sounds interesting . . .I would like to see what they look like.
If your talking about erosion of the supercharger impeller vanes they say its not a problem on belt driven centrifugals as the speed is slower than turbos and i've never had a problem in the past even though we didn't mist the injection as much as these newer styles.
We didn't talk to much about turbos but he did about injecting water between stages of diesel pullers, which the tractor pullers have been doing for over 20 years that I know of.
One reason I went with this company is they recommend imjecting before the supercharger which removes a lot of temperature were as other companys recomend after the intercooler.