General Motors Corp.'s top executives were clearly encouraged to talk a lot about product in their various presentations at the Management Briefing Seminars in Traverse City early last month, but Gary Cowger, group vice president for manufacturing and labor relations, manages to say a little too much. Giving a quick rundown on new plants and new products, Mr. Cowger offhandedly mentions “we'll be building the Cadillac XLR in Bowling Green” showing a slide of the high-end roadster based on the sexy Evoq concept car. What he apparently didn't realize was that although the name has been used a lot internally, GM's Cadillac Div. has not yet announced the official name for the new roadster, expected to go into production next year. A GM spokesman downplays the faux pas, although he acknowledges some Cadillac folks are miffed by the disclosure, in part because all legal clearances haven't been obtained yet.