You'll be looking at about 15-18hp for the exhaust if you install a cat-back exhaust and headers, about 12hp for the CAI, another 9hp for the under drive pulleys. He doesn't need a custom tune, tell him to get a DiabloSport power programmer and he'll be able to get another 18hp with that. Together, 52-54hp increase and 40-45ft/lb of torque.