I have run up to 21psi, all tested with the best performance analysis gear on earth (Race Logic VBOX3i) and (no retune), but hey I am "sketchy"
I have customer in NZ with 8 sec drag car who runs 36psi same system set up and water meth (no retune)
Numerous cars in Australia, running straight methanol with water/meth in front of the turbo (no retune) all make more power, run faster, and last much much longer
When I get a chance I will try to scan this article that ran this exact same system (following all parameters I stated) that showed "massive gains" in on road performance V's no performance gain for post turbo. This has not changed since the last 100 years, everyone who has tried it who is qualified in mechanical engineering all agree and come to the same conclusions
all others (not so smart or dare I say qualified to comment) call it a band aid