Handling issue/question, 2004 4.0 4x4

All new rear suspension components, new track bar, and new shocks and stabilizer bar within the last 30k miles. I did get rear ended about 20k ago, although the body shop reported no frame or suspension damage. But the handling did seem to get worse after that. Alignment is correct, tire wear is even and steering doesn't wander other than what's listed below.

Statically the handling is fine. When you get into a dynamic situation there is a drastic difference in the behavior. From cruise when letting off the gas, there is a definite movement to the right. Get back on the gas, and there's a definite movement to the left, enough to change lanes if you let it, sometimes quickly.

It's obvious to me that something is shifting in the suspension; to me it feels like the rear is moving, as sometimes when heavy on the gas there will be a squirm in the rear.

Wanted to pick the brains of those that might have an idea of what the problem could be with suggestions for possible solutions.

Thanks in advance.