2003 Chevy Impala Nobody can find problem!

Car has had a wiggle(bouncing?) In front end since I drove it off the used car lot. Car dealer and I between the two of us have replaced all 4 struts, both front axles and front wheel bearings, brakes and rotors all the way around, new tires, replaced rear sway bar hardware and an alignment. What's left that could be causing this? Every garage that has looked at said that they see or feel nothing loose or irregular, I'm about too just give up and just drive it with it riding horribly!