I have Patriot auger muffler inserts (
Patriot Muffler Inserts H3843 - Free Shipping on Orders Over $99 at Summit Racing) in 3.5" tubing - no packing of any kind, but a metallic sound to the exhaust which some don't like. If these rattle it's because they're not tight enough. I pounded mine in with a mandrel and a heavy hammer. I can't remember whether I used a 32 oz ball pein or a hand sledge, but it took some force. That was after the first attempt at installation when they were too loose and the rattling drove me crazy.