There is a sort of squeak when cold. I noticed this at a rally and the chap I was speaking to put his foot on the exhaust pipe and it stopped! I live with it rather than driving with one foot out the door!! :P
It is from the exhaust although it sounds rather like a water pump death rattle. Within a couple of miles it goes away. Just hold the exhaust before it gets too hot and notice the difference. Baffles apparently.