I was under the impression that 757's of all models said "heavy" due to the remarkably violent vortices they created? I have also heard that a 757 will throw off a more violent set of vortices than a 767. Not sure where I read this info - probably here. I am not sure if the pilots say "heavy" or if the controllers simply modify spacing on a 757 to heavy standards. Can someone shed light on this, and explain why the 757 has such a violent wintip vortex?