I've noticed that in the past few days that the car has a horrible shake around 35-40 mph ( even worse when I let my foot off the throttle.) When I apply the brake (lightly) at this speed it gets a little better. When i pulled over to take a look the caliper looks grooved ,more so than the other side.And you can smell the pads working overtime. I would like to upgrade at this point. I've heard of using 740 rotors. What about SS brake lines. Do they REALLY make a difference.What can I do to upgrade the rear also. Any help would be grateful