Well, it's stopped.
I'm not getting too excited about this, but it would be good to know what others have done about this, apart from change the Cat.
I may as well post my own previous on this.
I came out one morning years ago, started the car and got this death rattle, which seemed associated with rpm.
I had to go to work, so after checking the oil, I drove very gently- thinking, 'Me car is fooked!'.
After work I took it to 'A for Audi' in Clydebank, fearing the worst.
Andy put it up on the ramp, engine rattling like a *******.
He smacked the cat with a mashie, and the noise stopped dead.
I've rarely been more impressed, in a garage.