Just a few of the threads discussing the Flowmaster products in the last few months, should be a good start... http://www.xterraownersclub.com/ubb/ultimatebb.php?ubb=get_topic;f=70;t=000754 http://www.xterraownersclub.com/ubb/ultimatebb.php?ubb=get_topic;f=70;t=000790 http://www.xterraownersclub.com/ubb/ultimatebb.php?ubb=get_topic;f=70;t=000774 http://www.xterraownersclub.com/ubb/ultimatebb.php?ubb=get_topic;f=70;t=000764 http://www.xterraownersclub.com/ubb/ultimatebb.php?ubb=get_topic;f=70;t=000698