I've got a 2004 330 and had the same problem. The Rx models tend to drift left or right fairly easily. I took mine in for an alignment and it was better then when I first got it. The Lexus rx330 steering requires constant focus while driving. This vehical does not guide itself down the road, you have to constantly steer it. If you take your eye's off the road for a second it's liable to drift left or right very quickly. I would say it's a design issue but a front end alignment will help.