Wow, 400F, that's some serious heat! I get scared when I see anything over 200F in my car. Mine would go into meltdown at that temp for sure.
The WWII aircraft did inject upstream of the blower but I think it's because they used boost pressure to move the water; also, less parts (like a pump) to break down over enemy ground.
Hot air means higher velocity through the compressor and less drag. The water injection will alter the flow map, that may be why the owner of AIS sees higher boost with it.
So you are spraying in the compressor and after the intercooler? It might be worthwhile to weld in some more bungs downstream of the intercooler and move the nozzles from the compressor inlet so you can have a good comparison. I really think you will have water condensating into larger droplets inside the intercooler if you don't. I know, 400F is way hot, but 38lbs is working against the ability to evaporate the water. Water boils at 212F at 14.7psi. You are at 50psi actual; which brings the boiling point of water to 350F. I know it's an H2O / methanol mix but the same theory applies. So, even at 400F, you need the smallest water droplets you can get. As the temp comes down, the evaporation rate is further reduced.
For instance, a drawthrough turbo system will use larger carb jetting than a comparable blowthrough system because the compressor de-atomizes the mix.
I can't wait to see the EGT results; I hope they are even across the 8 ports.
Keep it going, I'll be looking forward to seeing it run again soon!