Hello all long time lurker first time poster! 2010 QX56 Had cats/exhauast manifolds replaced a year ago quited down a bunch! But still there's a bit of too much of exhaust sound. I am thinking it maybe the 2nd cats in the system as there is a vibration under my feet under excellaration and its the loudest in the drivers seat. One dealer told me the secondary cats can get louder once they get old (156,000miles on mine) but never throw a code and he thinks maybe that's it. Lastly it is all quiet until I put it in gear then it gets louder. If I go up a hill there's a slight annoying drone. Any ideas besides what I said? Thanks!