Z31 turbo?

Hey guys, how fast would a Z31 turbo be with say an intake, exhuast, and a turbo in good shape? I thought they were pretty quick, as my dad's Z32 tt is really quick, but i was kinda suprised by one a couple nights ago, and it wasn't that fast... or he was racing at like 9/10ths. Mid-high 14's? And would it die off some up top, say above 80mph or so? Just curious, and I'm not referring to a totally tricked out one, just a very mildly modded one. Thanks