The Stang that needed the silicon probably did....my 03 GT's windows when they work, seem to motor well. Most times when it gets really warm, my passenger window fails to work...sometimes pressing the switch back and forth on the drivers will get it to work. If it's really warm, it does not. Now, the driver's side is not working, but the passenger’s side is. In cold weather both sides work well...Therefore I know it's NOT the motors or switches, but more than likely it's a relay box located below the dash on the drivers side, upper left. When jiggling the driver’s side door switch, I can hear clicking sounds.
If someone actually knows what the problem REALLY is, I would also like to know...as it would alleviate a lot of frustration in looking.