Muffler rattle!!!
 

I have had a rattle noise that starts up when the car is warmed up and slowly pulling away under load.
I have narrowed it down to the stock muffler internals. Anyone had a similar rattle and know what it is in the damn muffler that is loose? and gradually getting worse.
It seems to be on the left side.
Thanks.

I have a rattle twice during my 5 year ownership of my 04 Boxster S, about 25K miles apart. Both times the rattle was due to a broken stud on the left side exhaust mount. Repair required removal of muffler and welding the stud back onto the muffler. Since I have a mig welder it was a relatively quick fix.

Thanks for the info.
Is there a way to check or prove it's this nut prior to removing muffler?

Mine made the noise while idling so I could just press upward on the muffler with a stick of wood between the floor and muffler and the noise would go away. That allowed me to conclude it was a mounting issue however only visual inspection will allow you to pinpoint the issue. First step would be to safely get under the car while it’s running and look and listen for any rattles and leaks. Could try using an engine ear. Check tightness of all mounting points and Muffler clamps. If that doesn’t resolve I’d remove rear bumper so you have a clear view of this mounting point. Again, this was easier for me because it happened even while at a standstill at idle.

Check the heat shields between the cats. The rivets rust out and they will vibrate against the exhaust. Use a rubber mallet and bang around to find the source. It sounds like a tinny rattle.

Solve it with a steel ziptie or a hose clamp. Had this happen on my first box.

I have rear cat delete pipes on so no heat shield. The damn rattle is inside or on top of the muffler. Maybe it’s time for a Fister exhaust😁