[rotrex]

pre throttle works well with non-charge cooled engines and in high boost applications (auch as yours). IMHO rice racing's air assisted spray works best for this purpose.
His systems inject a very fine mist in the air filter housing. This way the mist has time to travel and evaporate. Within the turbo. a part of the mix further evaporates leaving a extremely fine mist behind that actually has a chance to make it into the cylinder.

I have tried pre-turbo on a Rotrex C30-74 and a C30-94. Any jet bigger than a 03mm (75ml/min) and I got condensation indicated by IAT fluctuations (IAT sensor position past CC).

if done incorrectly, the water will be lost on the walls of the intake piping and you life of the methanol content.

So either air assisted spray pre-turbo (read his thread here in the stickies on top) or direct port in the proper location near the fuel injectors. Everything else is a compromise, albeit way easier to install and maintain. Most do not dare to tune to fully take advantage of high flow water meth injection in fear of a failure of the system.