^ This guy knows. I'd like a ride in your car one day.
Try increasing the dampers (i.e. making them a bit harder). Your springs are pretty stiff, and probably not that well dampened (considering the cheap dampers), expect a stiff ride.
I paid people at tyre shops to align my wheels, and my car drove worse afterwards. They also said that <insert tyre they are trying to sell> is better than what I have on my car, no, it's not. They also said that I couldn't fit 265/35/18 (on BNR34 wheels) on my car, psh. I would laugh at their faces if they told me to adjust the suspension height with the spring seat when I have base height adjustable struts.
I used to drive through Parramatta Rd on almost a daily basis with my GT-R. I had old TEINs on there, my gods it was horrid. At least the Ohlins installed now are more compliant (although not 'tuned').
FYI standard R32 GT-R spring rates are (from memory) 3 and 3.5 kg/mm (f,r).