I believe I have. It think it's the passenger cam seal and so do 2 other Lexus mechanics that looked at it. The thing is, it hasn't leaked since I've been driving it around. I cleaned off as much oil as I could and haven't seen new oil leak. What really sucks is that I did the timing belt myself 10k miles ago. I did not do the cam seals at the time because I read that they were difficult and required a lot more work as the extremely tight cams must be removed. One of the mechanics recommended that I continue to drive with it and watch the leak. He said if it's slow then just try to wait until the next timing belt change so that I don't have to drop $1300 on seals right now.
I am happy that it hasn't leaked anything during short drives around home but I am still worried about the fact that it leaked approximately half a quart during my 1hr 45min drive which did include climbing about 4,000 feet in elevation.[/QU
Pretty much the same thing I am dealing with. Changed the timing belt out almost 2 years ago and didn't do the cam seals. Just gonna watch mine till the next belt change..might run some high mileage oil with some seal conditioners to see if it helps. Probably wont help but its worth a shot.