I recall reading a few reviews that mentioned episodes in which the front tended to wander with the 18" wheels. I have noticed this - just a bit, but not to the point of rising anywhere close to a safety issue. Still, any ideas as to the cause or for a remedy?

An alignment check is a good start. It is covered under the warranty if you are within the mileage and time limits; check your warranty book.

I have a 2wd with 18s and it tracks straight.

Thanks, and I should have stated that it isn't an alignment issue. Rather, when the tires encounter slight differences in the road, I've noticed an unusual and slight movement that I've not felt in my years of driving.

yes I noticed the same problem when I first took delivery of the car. I brought it back to the dealer for a check and they said it is normal with 18" wheels. Well anyway it's not a big problem for me.

I am driving an M35iX loaner today while my fuel pump is replaced. I immediately noticed the AWD system doesn't like the ruts in the freeway and will wander around. A couple of times it was very pronounced and while accelerating the car felt like it moved over 6". On the same roads my 2wd with 18" tires tracks much better; you seldom notice the ruts and you never feel a direction change like I felt with M35iX. So after only 15 miles with AWD I am already looking forward to getting my 2WD EX back tonight.