bsalie99

I currently have my 2002 Z06 set up with VBP Sport leaf springs and Koni yellow single adj shocks. I was wondering if I would see an improvement if I switched to a Coil-over setup. the car is used for autocrossing 90% of the time and the last 10% is cruse nights. So I would need a set up for that , not just street use or open track use. I am in the New CAM class this year which made me switch from Hoosier A6's to Rival street tires and I still need to get the set up right, car is way tail happy now. I also have a 36mm front bar and an running 18x10.5 OEM wheels and 315's in a square set up

autoxer6

The change from leaf to coil doesn't really matter. You can dial in corner balance easier with coil, and you get some more roll stiffness with leaf. One isn't better than the other, just different.

Koni's are pretty darn good. The jump up to Penske / Ohlin / etc will make the ride nicer, and they are easier to adjust and set up. You wont see much of a lap time improvement though.

Your 36mm bar is big. You may be inducing corner entry understeer which then translates to snap oversteer. I would try a smaller front bar (like a 33mm) and do this before you change anything else. The bar is $150, shocks are $4,000, start with the cheap part.

lefrog

Stiff front bar + large front tires, I'm not too surprise the tail is moving around.
Coilovers will only help on bumpy courses were you can get crosstalk in the leaf spring. However there is no magic, if your bars are too stiff or your spring setup is not right, coilovers won't fix anything.
There is a slight weight saving going to coilovers. You can find used LG GT2s or Pfadt SA for about $1200 on the forum.
Going back to street tires, make sure your alignment is less aggressive than for your A6s and you might want to try a smaller bar in front and/or run smaller tires up front.