I recently purchased a 2005 Saab 9-3 linear 5-speed. There is a rattle noise coming from under the hood when I accelerate and shift. The noise only lasts 10-15 min until the car heats up, then it is gone. I work at a car dealership and a technician thought it was my heat shield, which was loose, but we removed the shield and the rattle is still there. Any ideas? It is driving me crazy. It sounds like tin can full of rocks that is being shaken. Any tips would help. Thanks.