When the water collects in the filter, then passes through, it creates droplets. If you're going to inject, you want a mist to enter the TB, not droplets.
You can't control it if you're trying to get through the filter first. Why not spray the radiator, and lower your ECT temps that way? Some intercooled rally cars do this for the intercooler heat exchanger.
Also, if your IAT gets wet, it will give false cool readings, and your PCM will constantly hunt for the right balance. Inject a mist AFTER the IAT but before the MAF. Your intake air temps don't start really increasing until they get into the engine anyway.