I love forums. There is so much information to be learned.
I have had my 2007 RX350 since August of 2006. My wife and I were pretty excited on the first night of ownership, except for the fact that she had a real bad coughing attack on the way home. We chalked it off to a lot of allergy related stuff in the air in the NW suburbs of Chicago during the summer. Little did we know that these coughing spells would be a very big part of our lives in the next 32 months. The weird thing was that if my wife was sitting in the front passenger seat, she coughed hard and was miserable. No so, from the drivers seat. I brought this to the attention of the Lexus dealer on our first service visit, as well as the other 6 or 7 visits since. Each time, they somehow managed to change the air filter element (mostly at no cost) and did admit that the filter housing is behind the glove box and is where the main fresh air enters the car. On one long road trip, she put her feet up on the dash for several minutes. I didn't much think anything of it, except the next day, there were all these white marks where her feet had been. We both thought that was very odd indeed. Her coughing got so bad that I found myself in the passenger seat most of the time. Our drives in the RX350 were becoming uncomfortable for my wife, even in the drivers seat. I continued to complain each time I took the car in for service, but all that could be done is change the filter element...with no positive results.
Then I found this thread and everything has changed. I read with interest about the "white dust" on the dash. Hmmm, the same stuff that we saw on our dash. Now some answers were finally realized, thanks to these forums.
I just got off the phone with my Lexus service rep. I had all these notes about the evaporator core, but before I could finish explaining my call, the service rep said, "when can you bring the car in"? He stated what I had learned about the job being labor intensive and offered the loaner. I also mentioned about the residual dust being in the venting system and he assured me that everything would be taken care of after installing the new, non porous, evaporator core and cleaning the ducting areas.
I will be interested in seeing how much this fix helps my wife. I am also interested in any information out there pertaining to the possibility of problems inhaling the "aluminum hydroxide" flakes from the old evaporator core.