I found that removing the heavy front bumper really helped the 280Z feel more like a 240Z in the steering/handling department. Loosen the front sway bar end links so they have a tiny bit of play in the bushing stack, play with tire pressure, tighten up the rear swaybar bushings, try trail-braking, try -1.5 to -2 degrees of front camber if possible, lengthen the T/C rods to increase caster (I used a couple of thick washers), set front toe to near zero, and last but no least, don't turn in has hard when entering the corner.
Oh and search hybridZ. Lots of info about understeer.