I need help!

I have a 2004 roadster bought it new. From the start I've had a rattle coming from the transmission area when out of gear and clutch out; especialy when turning the motor off. Sounds like a metalic rattle. Took the car the dealer on few occasions. First was told it's normal, then they told me it was a throwout bearing (got that repaced and the clutch upgraded to a Nismo) then they repaced my transmission !!!! The rattle is still there!!! I feel bad for taking it back again!!! Anyone have/had this ? if so what's the remedy? Help!!!

 

check the heat shield.

 

Car in neutral, clutch out then turn it off. Sounds like marbles rattling around in a tin can, right?

The dealer was correct the first time - it's normal. We went through a half-dozen new Zs on the lot listening to the transmissions before realizing they all do it.