I hear it most when idling, i dont seem to hear it when driving but doesnt mean its not doing it - im not sure, someone told me it might be a loose heat shield or something to do with motor/exhaust area... but not sure how credible that is. and it is decently loud, i mean i pulled up to a taco bell and i mean it wasnt so loud that i couldnt hear what they were saying but i could definately hear the noise... but i mean that was with the wall there, when sitting at a light i can hear it from inside the car even with windows closed..
just to let you know i really appreciate your interest in my problem