How does meth injection work?

Can you control when it begins to spray?

Whats the best mixture? 50/50?

Whats the best brand?

Also what pulley could i drop to?

I just want to find out more on meth injection because i dont know much about it and was considering installing a kit on my DD. Current mods: SSAC headers, 3 in dp, k&n cai, stage 1 hv throttle body, 3.4", dhp pcm. Would it be better to drop pulley and add more boost and less timing? Or keep the 3.4 and add timing with less boost?