after closer inspection, i do not think it is the exhaust. if you open the hood, you can VERY clearly hear the noise coming from the engine. if i had to guess, its the engine closing the throttle bodies for some reason (idle?) also, after several revs and listening, the sound is very mechanical sounding, like a valve is shutting, and it is at the same rpm every time. i think you can just HEAR the noise now, and that the stock exhaust covers it up.
