04 Mustang, slow to return to idle.

I have a 04 Mustang with the 3.8L V6. Also this has a 5 speed manual trans. I find that when I drive it a little aggressivly and
rev to about 3500 and clutch to shift to the next gear the RPMs are very slow to drop. This means I have to wait to let the clutch out or the engine is still reving and makes the car lurch. It seems the revs really drop slowly until it falls below 2000.
Took it back to the dealer I bought it from and they checked it and drove it and told me its normal. Also they said there are no bulletins or such on it.
Any advice is appreciated.
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