[fredjacksonsan]

I'd check tire pressure first. A few pounds difference will give you a pull in either direction.

Also, when on the highway check the camber, or slope of the road you're on. If it slopes to the left your vehicle will want to go that way. Try driving awhile on a road that slopes to the right, and see if it pulls that way.

If after both of these it's still pulling, pull over after several minutes of driving, and feel the front wheel on both sides. If the left is noticeably warmer (or hot) compared to the right, then your caliper is sticking. In this case I'd have them replace the front caliper and brake shoes - definitely a warranty item.