I tuned a built 350Z Rev Up a few weeks a go , chap drove over from Denmark for Abbey to tune his car, rods/pistons/Cosworth cylinder heads/cams, headers , Cosworth Plenum, basically had the Cosworth kit fitted, after extensive tuning it had gain around 30bhp over a stock Rev Up car, all the torque/power over 4500 rpm.
I think for the same money but using a S/C you would of gain around 100bhp over a stock car and not had to work the car so hard.
NA tuning for big bhp is expensive