This isn't really so much a problem than it is just a question:

I have a first gen G37s 6mt, and I've noticed that when I'm backing off the throttle while in gear, there is a shuddering from the engine that happens when coasting down, from roughly 3300 to 3100/3050, then goes away.

There is no change in handling or performance. If I were to stomp on the gas while it was doing it, everything responds normally (from what I can observe).

Any ideas on what it may be???