I made a video to show you guys what I am talking about.
http://www.youtube.com/watch?v=MDam2tMye1A
by the way I have noticed that it doesn't seem to ever do it for the first couple minutes of running, but after that it gets steadily worse. The motor is not getting over 100 degrees F, and the ESC is not even warm. This is on 6s. Hottest I have ever had the motor was about 130 after running the track for a while. Telemetry data from the DX3s.