Meth injection with distilled water is useless. The main reason is that water you are spraying will likely be at the same temp as engine bay. It won`t cool enough incoming air. It will also gives tons of white smoke at the tailpipe. At least the valves will be cleaned from carbon deposits and shine like new.

The reason methanol is needed is that when alcohol evaporates it ingest heat and cools the air making it more dense, with more oxygen content. So to make it work you need a real methanol in that injection. Wrapping headers with thermal barrier will also bring underhood temp down, or cutting vents in fenders or hood and adding E-fans.