[Iflylow]

GM brake rotors are known to be junk, and not just on the Impala. Turning them just makes the problem worse because you are making them thinner and less able to absorb the heat. They then warp even faster than before. Get rid of them and get some quality rotors and pads, and your problems will go away. I use rotorpros on ebay for mine, and have had no problems. Others say R1 Concepts are good. Generally, any good brand should be better than GM.
When the rotors are replaced, look at the caliper guide pins. Make sure they are straight, not worn out, and are lubed well. Also make sure the rubber boot around them is in good shape.
A tire out of balance could cause your vibration. Get it checked out, if that doesn't fix it, post again.