That makes sense. Look at the Outlook, it gains 5hp going from single to dual exhaust. The XE is rated 270hp and has theMichael_S said:In another discussion forum, someone asked how the Outlook and Acadia manage an extra 20 horsepower from essentially the same engine. The assumption was that General Motors made some sort of technological improvements for the Outlook and Acadia but did not make them available on the sedans. The response - which may or may not be nonsense (this is the Internet, after all ) is that the Outlook and Acadia engine do not have any sophisticated technological enhancements. What they have is a lot more room under the hood, so they can fit a much larger and more free-flowing intake and exhaust setup than you can fit in a sedan.