First, congrats on owning a sweet car!
Does it make this noise everytime you start from a stop for the first 5-10 minutes?
How many miles on the car?
How long does the noise last?
On a cold start can you try this tomorrow.....
Start from a stop the way you normally would then use the ebrake to stop the car and listen for the noise. Do this a few times to see if the noise continues or disappears. I have seen some weird noises come from the brakes on first startup... not particullary on the Speed6 as I don't see very many of them. But I have seen it on the regular 6 and the 3. This will help us eliminate a possible source of the noise.
The exhaust donut is another possibility... but lets check the brakes first.
Nope! Does it make the sound in reverse?
Try a couple free spirited accelerations in reverse and then go into 1st and listen for a change in the noise. Typically if the exhaust donut is making the noise the reverse accel will help to reseat it and may temporarily remove the noise.
Good question, I'll have to try it tomorrow. Any other areas that may cause this noise?