Toyota can't reproduce the problem (as expected) so they aren't interested. Getting video of a pretty random event going on behind you while you are driving is somewhat difficult! However, I do have a poor quality video that shows one of the smaller clouds of smoke. It does look grayish on the video. I have yet to show this to Toyota, but seeing this thread updated with further information has encouraged me to try again when I get some time to take it into the garage. Thanks. I will let ever