True, the majority of people stick W.I. on top of an engine running extremely rich and then they complain that W.I. is useless (or even loses them power)
I did dyno runs on mine and only started seeing pure gains as the AFR dipped to 12:0 and beyond (13:0, didn't have the nerve to run leaner under full boost
ops: )
Adding water as the AFR was 10.5:1 did nothing for extra power - didn't lose power either, as I was way beyond the manufacturer's limits. At 12.5:1 I was looking at 8% more power with around 10% water/fuel ratio.