:( I also own 2005 ES330 and I've experienced same problem with my heater, and the chemical, burning-wire like smell doen't go away at all. I constantly roll down and up windows to let air changed during extended drive on highways. It's really annoying and makes me worried if it's bad for little ones in the back.
I already changed cabin filter twice to see if it makes difference, but no use. Dealer couldn't find any problem and they just applied some sprays in the vent.
If anyone can give me an idea to fix this problem, I'll appreciate.
