You are correct. The Roxor also has a catalytic converter. You can plug it if you use the wrong diesel. Or addatives like marvle mystery oil, trans fluid etc. So be careful. On my 2006 dodge I drilled out the center of the catalytic converter with a 3" hole saw. It didn't have sensors monitoring it anyway. Worked out well and reduced the restriction. Might do that or remove it all together on my Roxor when I get around to it.