Has anyone done this? I just changed form a 3" straight to a 4" from City Muffler and Performance. http://www.mufflerandperformance.com/ Off E-Bay $315. (Good service) This is an improvement, but there is still a drone at highway speeds. I did a search and came up with TDR'ers with the same problem, but found nothing about a 4" resonator. Just from people who enjoy headaches that have removed their stock ones. Thanks for any answers.