While removing the factory down pipe I noticed a copper nut loosely attached to stud. It was behind the mounting plate for the downpipe. For some reason there was only one on the passenger side of the downpipe. There was also a stud on the other side of the downpipe. The other stud had no nut. Very peculiar since the nut was copper. The nut was also about 3/4 deep. Any ideas what the function is?