Thats the heatshield around the cat.. good work on finding it.

Yeah good job.

Hope your cruising is rattle free now!

not sure if this applies to your situation or you model of falcon but I finally found the cause of one of my suspension noises/issues a while back. A chunk of gravel was lodged between the lower swaybar link bush and the lower arm itself and it wasn't visible, every time I took the front end apart I always took the swaybar off the top bush of the link (so the links themselves always remained connect to the lower arms), it wasn't until I stripped the threads on the links and had to get new ones did I discover the pebble lodged in one of them, was just happy to have fixed another problem at the time I'd spent bloody ages going over the whole car prior lol all because of one little pebble.

I'd look everywhere possible for it, it could be anywhere, or maybe just keep driving the car through a puddle until it washes off.

They're stuck in my cat converter

They ended up coming out, I drove it an hour into the country and drove really slowly up a steep hill, was going about 10k or so and they all feel out my exhaust, was really loud t the time haja but I'm rattle free now