Z1 GT675 kit i hit the same boost (that you hit at 5000) at 3800-4000 rpm. But i guess it depends on mods. I had 400+ cams and MSP manifolds. Well i think most things are still listed in my profile. Now i gave GTX2863`s and 500 cams and hit full boost at 4200. Is that a dyno that can hold load or is it just one of those useless interia dynos?