Muffler Bearings
Contrary to popular belief, muffler bearings do exist, just ask your local dodge stealth or mitsubisi gt3000 owner. Although a popular prank to pull on the not so automotive savy muffler bearings are located inside the muffler, in order to operate a flap which opens and closes depending on the exhaust flow directing flow back into the turbo. Due to inconvienience (carbon/other buildup often jammed the bearings causing noise and poor performance) the bearings are only found on older models.