Congratulations, your chassis is now allowing your suspension to do more of the work!

It will take some getting used to, and likely some adjustment somewhere to bring back into balance. Your suspension was having to compensate for a lot of chassis flex before, now it's not. The suspension is effectively stiffer than it was, especially in the rear. So, if you have a rear swaybar, backing it off a notch might help.

Or, it could be as simple as changing the alignment, or even the tire pressures. What about shocks, are they adjustable? A little softer in the rear could help.