Im looking to order a twin turbo kit for my g35 what other mods do i need to go along with it that is mandatory and do i HAVE to have the engine rebuilt?

In terms of engine modifications that all depends on the level of power you're looking to attain. I know the VQ's can handle some power, but once you get past a certain point you'll have to start upgrading engine internals.

Without upgrading the internals, you're for sure looking at increasing the capacity of the fuel system.