I was looking into getting a new exhaust and i ran across the Stainless Steel XR-1 Long Tube Headers by Borla. http://www.4wd.com/productdetails.as...&partID=43609# its not street legal but my question is: The lack in back pressure from the removal of the cat converters cause long term damage to the engine? and what kind of power gains do you think are in it?