so i have a 2005 cobalt ss stage 3 making 266 whp/244wtq currently. i want to know how much power i will get if i put on a ported head and stage 2 cams from ZZP. they have told me 20-30 but that sounds low. does anyone know what gains i should expect?

 

sounds about right. On an m62 most people top out around 300whp. with a good tune and supporting cooling, you should be able to get up in the 290-300ish range