good till about 650whp. so I would stay around 600 and under to be safe. Fully built gt3076'r turbos 744 whp @ 26 psi so far. Stock fuel line with all rubber hoses replaced with gates barricade, Twin Walbro 255's, stock rail ,Nismo 740's with additional Throttle body fuel injectors for added fuel on top end. I will be going top feed this spring! :-)