I have the same problem as well and its driving me bonkers! I drive a 06 g35 coupe M6 and every time I pin down to accelerate in any gear at low rpms I hear a rattling noise. I'm leaning towards the tranny or drive shaft. They say these transmissions are very loud... Sounds more like a main bearing that holds the drive shaft to the bottom of the car that has gone bad or something. What u guys think?

 

I had a major breakthrough on my 2005 6MT Coupe with this low-RPM acceleration rattle issue, and it may be of help to others. Two weeks ago, I replaced my brake pads all around. In the course of the replacement, I noticed that there was a good amount of loose rust in the caliper pistons. I knocked the rust out, not thinking much of it at the time. Replaced the pads, and as I was bedding them I realized my low-RPM rattle was gone.

It's been about two weeks now, and the rattle has not returned. It's completely gone! Now I'm just waiting for cooler weather so I can enjoy driving with the windows down again.

 

interesting, I also have the same rattling noise under hard acceleration. i thought it had to do with the type of fuel i am running. Guess not.