So I got the car in May and if let off the throttle my car vibrates. If step into it or press the brake, it stops. I've replaced the u-joints. What else could be wrong?
Actually, yes it could be motor mounts... Or it could be an improperly balanced driveshaft, bad control arm bushings, improperly balanced tires, or a number of other suspension / drivetrain related issues.
Control arm bushings, in my experience, is more of a rattle over bumps. What you described is how my old 96 GT acted when the motor mounts were messed up after an accident.