Annoying rattle

I am trying to trace the source of annoying metallic clinking from the rear of my C4S. Any ideas would be gratefully received. It isn't really noticeable when the engine (exhaust?) is cold, but after about 4 miles of open road driving it is obvious enough. It gets a bit louder when the the engine is fully warmed up, but not so bad that it gives me a major concern I have a switchable Porsche exhaust on the car and I think the noise is less obvious when the quiet mode is selected. So my suspicion is that is is something to do with the exhaust and possibly its connected to the flap Its also more noticeable under hard right hand cornering which may be something to do with the system being stressed in some way?

i have what sounds like the same noise in my car a 996 Turbo S, it obviously hasn't got PSE. My first thoughts were heat shields as these often corrode, but its been into OPC and were unable to trace it. with the radio off its more noticable but with it on it isn't. I've also been out with a rear seat passenger to try and locate it without success. Hope you get it sorted and if you do let me know!!

Although nice to know I'm not alone, not so good to hear that attempts to track down the problem have not been successful. Why do I always seem to have problems like this! My car is due for service fairly soon so will ask my dealer to have a good look round underneath.