+1 on the above
i used to have the gt3040 with a machined out .54 rb25 housing and that was still laggy, then i went to external gate with a .82 rear and that was even more laggy, you wont start making boost until about 3,800-4,00rpm
i dont think you will get the response u want but u will get a big hit of boost
even with a .63 housing it will still be laggy on a stock motor