One other thing you may want to consider is how old or how many miles are on your ps pump. I have heard of people having problems with worn out ps pumps causing the engine to try to die.
But probably the case here you likely have bad motor mounts. No one is crazy here. My 91 SC used to fibrate at a stop in gear like a moefoe but once I replaced the motor mounts all was better. It was amazing what kind of difference it made. It felt like a completely different car.
Shane