I has just changed my plugs wires and coils the week before I took it into the shop.

 

i have the same problem i guess. whenever i hit high rpm's its sounds like something is shaking around. almost like something is loose. at first i thought it was the engine cover cuz it was loose n i took it off and it still happens. i guess ill try the coils wires and plugs too, and maybe even a new greddy pulley

 

If the sound your hearing could possibly resemble the now infamous "marbles in a can" sound, I'd be looking for a good compression test first...

 

idk i have an 07 and when i hit about 5500 or 6000 rpm when getting on it, i hear a "noise" under my hood. i upgraded to ignition solution form mazsport and i still hear the noise. i have heard the noise since i bought the car brand new. havnt had it checked out but. i did the throttle body bypass still there. i dont have any rx8 owners around to hear if there car does the same thing.

 

well the sounds is gone lol i took my engine cover off when i drive n the sounds disappeared. i guess it was juss the engine cover raddling

 

i got the same type of noise and nailed it down to the f n shutter valve under the intake ports .dealer has no listing for the part and says i need a complete intake from the front to the back...damm i'm pissed!