i just changed gas to 93 at shell, and i havent heard the noise yet... i drove the car up to around 4500 rpms, and didnt hear anything. i was somewhat afraid to go further from what i had read earlier in this thread.... maybe it was just the gasoline that i got earlier? i will drive it again tommorow and see if i can hear the noise, if not then maybe it was just the gas that i used.... should i get it checked out anyways?