Katrina heads for Gulf Coast at 160 mphBy MARY FOSTER Associated Press Writer NEW ORLEANS (AP) -- Coastal residents jammed freeways and gas stations as they rushed to get out of the way of Hurricane Katrina, which was upgraded to a Category 4 storm Sunday, with sustained winds of 160 mph, the National Hurricane Center said.The massive storm appeared headed for New Orleans and the Louisiana coast."Ladies and gentlemen, this is not a test. This is the real deal," New Orleans Mayor C. Ray Nagin said at a news conference. "Board up your homes, make sure you have enough medicine,...