Shaking and rattling noise! Please Help

I have a 2007 chevy cobalt LT. I have taken it everywhere to get fixed and every time its something else so I get it fixed and its still not the right thing. Ok so the car I can just sit there and wiggle the stearing wheel and hear a nocking noise and can feel it in the steering column and left side. While im driving and hit a bump I feel and hear it rattle and the steering goes slightly loose. I will hit the brakes and the steering wheel will shake and I can feel it in the pedals and front left tire and steering column. The sound sounds like its coming from right above the pedals. I have it at the shop now and they think its the rack and pinion bushing. Any ideas? I have had the control arms replace and bushings, sway bar bushings and links replaced, all new shocks and struts, rotors and everything smoothed and cleaned, tie rods and wheel bearings.