Diff Bushings won't affect the what it feels like you have.
If it didn't feel that way before the subframe bushings were installed, but it does since, there is something going on with them likely.
Do the marker around the bushing where it mounts to the body, see if the bushing/cradle is moving in relation to the unibody.
2012LS3VERT i've never installed your bushings, are you supposed to install them with the metal retainer plates that are on the OEM bushings?