Bounce is down to the dampers.
Springs will always bounce if the dampers they are working with arent able to absorb the energy.
Also, if your suspension arms arent properly located, for example because there is play in a balljoint, this will make the car "rock and roll" in an uncontrolled, wobbly fashion.
Oooh and things like knackered top mounts too. All contributes to bouncy crashy horridness.
And, chillbill, careful with the amount of lowering you're planning; B6s arent designed for that amount of drop.
Would suggest coilovers?