If as you say, 'everything was done perfect' try switching the left and right-side front rotors and see if the 'pull' changes sides. G.M. sources their parts from a host of suppliers, and cast iron from different batches sometimes has different coefficients of friction. On some 'Vettes, this has resulted in pulling in one direction with all-new parts installed by dealers, when one new rotor came from a Michigan foundary and the other from Alabama. This is also why you can run into trouble changing only one front rotor at a time. Brake pads don't exhibit this difference.
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