Speaking of Freightliner... see section re: mufflers... <a href="http://archives.fleetmag.com/publication/article.jsp?pubId=1&id=118" target="_blank">http://archives.fleetmag.com/publication/article.jsp?pubId=1&id=118</a> and this one... <a href="http://www.vhtrucks.com/pressemission.htm" target="_blank">http://www.vhtrucks.com/pressemission.htm</a>