Ok lets say street legal Z car ! not my car , I can't take to out to Nv. and run it, Here is mild build RB25 90mm throttle body and bigger turbo ,can boost up maybe 375hp or more as is .here is where gets hairy ,has stock 330 ratio and pulls hard all gears . I can say I believe 175 mph or more as is ,if your nads can hold on.