Why does my car vibrate really bad when I.

Most common cause is a worn spot inside an inner cv joint housing. That can show up and / or be aggravated by anything that changes where the large rollers run back and forth in their slots as the half shaft rotates. A collapsed engine mount will cause that change in half shaft angle and effective length. Also, readjusting the engine mount(s) that set the side-to-side position of the engine will affect that. Another common problem that only affects GM front-wheel-drive cars is if any repair work was done that required lowering the engine cradle. It is extremely important that the cradle be reinstalled in exactly the same location. If it is not, the alignment will be affected and having the car aligned will not solve the miserable handling. The potential for the vibration under acceleration to show up is not CAUSED by shifting the cradle. That problem is there already, but shows up due to shifting the cradle. That puts the inner cv joints' rollers in different areas within the housings causing the rollers to run back and forth in and out of the worn spots. The binding is caused by the torque from the engine, and prevents the rollers from moving freely. That causes them to push in and out on the spindles which are connected to the steering linkages and steering wheel, so all of that stat stuff vibrates.