Exhaust making wierd sound, help..

I just recently noticed this problem on my 97 trans am. when the cars in drive, the exhaust sounds normal no matter what rpm im at, but just the other night, the car was in park and i had my friend rev up my car a bit, and i noticed that this sound was coming from my exhaust every time he revved it high while in park. it sounded like a rock was bouncing around my mufffler or something. it seemed to only happen while its in park, cause i never noticed while while driving before. does anyone know what this could be?

Check the cat. If it had solid media it could have broken up and may eventually block the exhaust resulting in greatly reduced performance. Often times after the convertors get so old they will solidify due to repeated heating and cooling and they will break up. If this is the case you will need to get a new one.

hey edd jack up the rear of the car and search your exhaust from tip to the cat and make sure there are no little metal clamps/wires/straps loose. i had some sort of id tag dangling and it made that same sound. give it a shot