check your tire pressure make sure the fronts are the same and the rears are the same did u get a print out of the specs??? was it alinged with a full tank of gas ? did they weigh down your car ? coulud be a caster problem.
If the caster is out of adjustment, it can cause problems in straight-line tracking. If the caster is different from side to side, the vehicle will pull to the side with the less positive caster. If the caster is equal but too negative, the steering will be light and the vehicle will wander and be difficult to keep in a straight line. If the caster is equal but too positive, the steering will be heavy and the steering wheel may kick when you hit a bump.
or the sai (Steering Axis Inclination) whats your sai ??