so i just went in for my first service and my car feels brand new again. but now when i go to 8kish i hear a hissing sound that was not there before. should i take it back in or does anyone know what it is? only happens when im moving, not reving in place.

http://www.rx8club.com/showthread.php?t=102244&highlight=rattling+noise
Maybe that will help. I get the same thing, but not all the times. It seems to be coming from the passenger side dash area when i rev 8200 rpm and higher.

yeah. i think thats where it is coming from too. thanks for the reply. thought they didnt tighten up something enough. phew.

The noise that you've heard came from the heater core.