I’m hearing a lot of good thing about ZZP and I have a question I’m new to the supercharged cars. But I do want more HP and I was looking at the injectors and the pulley, but I see that there different size pulleys, witch would be the best pulley and what’s the difference in the sizes?

I heard that 2.9" was the best with stage 2, but if you go with bigger injectors you can go smaller (of course). I think a 2.9" will get you like 1.5 lbs of boost or something like that. (Don't quote me on that) I dunno if that was what you were looking for, but at least I tried.

42 lbs injectors 2.9 and up to 3.1
60 lbs injectors 2.5 and up i believe with a lot of cooling mods

Thanks on the info guys but one thing, when I add this would I need the HP tuner how does work?

if you dont get the gm stage 2 kit yes you will need a tune wether its by a company but hp tuners is reccommened