Some time back now I cut out the secondary cats on my truck and I got better MPG's and my truck was way louder, exactly what I wanted. There was a tiny bit of a rattle sound that I would hear at certain RPM's but only under load. So I decided that it was a frequency rattle and checked all of my heat shields. As time went on it got worse and worse. Finally it got to the point that I wouldn't shift so that I wouldn't hit those RPM's. I took it to a friends shop and we found that it was the muffler gone bad. Something inside the muffler had broken or somehow become unattached and was rattling in there. So I called up Banks and they sent me a new one. I got it all installed and the rattle was gone. Now I have been driving for a few days and it is slightly coming back. I'm wondering if the extra heat from the cats being gone is damaging that muffler. I would like to hear from some of you guys that have cut those cats out and what do you have for a muffler. I was considering going with a CherryBomb Extreme if this one doesn't work out.