[blue00gt]

Unfortunately the heads, cam, and intake are very restrictive on those cars so he will see very little gain adding things on the intake and exhaust side since those things are not the bottleneck. I would guess no noticeable gain from the CAI and maybe 5-10 rwhp from the O/R x-pipe.
You can get the stuff for a PI swap (heads, cams, and intake from a 99-04) and that would net him a nice gain. Unfortunately, with the stock heads cam and intake even a supercharger on those 96-98 GTs doesn't get you as much power gain compared to other mod motors.