So last night i hit around 120+ on the highway. i have a pretty much stock rx8 with a catback and midpipe and a modified airbox. After i hit that speed it sounded as if my tire was loosing air really fast until i came to a complete stop. and the noise came back after taking off. i turned the car off for an hour and the noise went away a little but today it has been perfect until i went back on the highway. now it has a bit of a hiss and a clanking noise coming from the rear. any clue?

Also on a seperate not does anyone know how to get rid of the blinking dsc and solid traction control light? I tried turning the wheel from side to side and there is no code.

 

Sounds to me like you have a bad wheel bearing. That can give you a noise. And also if bad enough will blink the tcs light. It uses the ABS sensors to get a reading. Is the ABS light on too?