i totally agree it transforms the engines behaviour ive had 2 t4 ybs, proper rs500 t4s one ported head and one standard, standard head was strangled and surgeing until 5500rpm then it was fine whereas ported head pulled smooth 28 psi straight in no surge. i guess it depends if you want an all out no expense spared build or cheapest bang for buck.
op if you can afford it full head job and gt3071, or biggest gain for smallest ££££ wack on a gt3071 and sell the t34.55.