My E90 felt light, floaty, whatever at the top of the backstretch at VIR. All cars are going to be 'light' here but I did feel it wanting to wander around a bit. This was when I had the OEM shocks with Dinan springs. I was running EDC in the Normal setting. When I switched it to the firm setting the car felt more planted. That is why I recommended to OP try that.
Now with my KW coilovers it feels planted all the time.
2013 E92 M3 with ESS VT2-585 SC, StopTech BBK, ESS Full Exhaust, and a bunch of carbon fiber ...