92 Buick PAU

I have noticed lately when driving I have little power at all times. I hear a clanking under my seat and at 50+ mph the car rocks and shakes. A friend has told me it could be the injectors being clogged. The turbo does not seem to work but that could be because of this other problem. The car has 216k miles but is in great shape. I have been told it could be the cat convertor, ign wires, coils. ????? Please help. Thx, Barry