I have my suspension set up pretty mild for the street, basically stock settings, a little more negitive camber and a little more caster. I have no aerodynamics work except a xenon from lip, which is not reinforced with a splitter right now.
The fastest Ive had my car is 125 or so and it is very solid. I feel the same as others, if you are having issues at 80-100 there may be some other issues you need to look at. My car is lowered about 3" and has 250/275 springs, with illuminas
I had my old 260 to between 150 and 160 a couple times, who know how fast it really was since i was using the stock tach. Over 140 WAS scary, i would say in the z cars i have driven things start to get scary in the 130-140 mph range.