not a pinging, more of a rattle

hey guys, im just concerned about this noise that my 1997 thunderbird. with the 4.6 is making. everytime i drive by another car or a wall or something, there is a realy bad rattling noise, sorry, its hard to explain, but its annoying. its worse with the a/c on. you can hardly hear it inside, but with the windows down, its very noticable. it used to happen only when i floored it. but now its everytime i barely step on the gas, its a constant noise and im trying to determine if its going to need attention soon. its definatly from the front of the car, cant really determine pass. or driver side though. any help is greatly appreciated. thanks.

could be the timming tensioner(can't spell).

is it possibly the gas that i use, i run 87? just a thought.

Does it sound a lot like a diesel engine? If so, then definitely use a better grade of gas. My Bird won't use anything but premium without the deisel sound happening upon acceleration (thanks again to whoever pointed that out to me!).