The car is a 2004 MT and I haven't had it very long, I do know that the engine was replaced shortly before i bought it and has around 12 thousand miles on it. I've began to notice that on very hard accelerations between 6k and 9k i hear a gravelly noise coming from the engine bay. When accelerating slower yet still all the way to the top of the rev band no noise. Any ideas on what that could be?

 

I have heard the same thing with my car I figured it was a loose exhaust sheild under the car.

 

If you search around here you will find two that pop up one is #7 on this forum read...

https://www.rx8club.com/rx-8-discussion-3/please-help-potential-new-owner-question-miac-181950/

The other one on here is MIAC (Marbles In A Can) sound. It is the noise that a Rotary engine makes when it is pre-igniting known as "ping" in the piston world. If your rotary is not happy with the octane of the gas you are using it will at first sound a little like the ping of the piston engine. Then if you push it harder....ask for more power it will sound like a marble shaken in a can. It is very damaging to the engine and it's apex seals. So it the noise lets up when you ease off the accelerator then it's Pre-ignition and you either need to run higher octane gas or have your engine de-carboned.